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Students can Download Chapter 7 Transport in Plants Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 7 Transport in Plants

Translocation:
It is the transport over longer distances takes place through the vascular system (the xylem and the phloem)

Means of transport:
Diffusion:

• It is passive process takes place from the regions of higher concentration to regions of lower
• Diffusion is a slow process and is not dependent on a ‘living system’, it mainly occurs in gases and liquids.
• Diffusion is very important to plants for gaseous movement within the plant body.

Rate of diffusion:
Factors influencing diffusion are

1. Gradient of concentration
2. The permeability of the membrane separating them
3. Temperature and pressure.

Facilitated Diffusion:
Substances that have a hydrophilic moiety difficult to pass through the membrane, their movement to be facilitated by protein.

What is the requirement for facilitated diffusion?

• Special membrane proteins help the movement of substances across membranes
• Movement of substance takes place without the expenditure of ATP or energy.

Rate of facilitated diffusion:
The diffusion rate depends on the

1. size of the substances.
2. solubility in lipids

Features:

1. Substances soluble in lipids diffuse through the membrane faster.
2. It is specific and allows the cell to select substances for uptake.
3. It is sensitive to inhibitors which react with protein side chains.
4. Transport rate reaches a maximum when all of the protein transporters are being used (saturation).
5. The proteins form channels in the membrane. Some channels are always open others can be controlled

Nature of transport protein:
1. The porins are proteins that form huge pores in the outer membranes of the plastids, mitochondria and some bacteria that allowing molecules up to the size of small proteins to pass through.

2. Some of the transport protein rotates and releases the molecule inside the cell, eg: water channels – made up of eight different types of aquaporins.

Passive symports, antiports and uniport:

1. In a symport, both molecules cross the membrane in the same direction with help of carrier or transport proteins.
2. In an antiport, they move in opposite directions.
3. When a molecule moves across a membrane independent of other molecules, the process is called uniport.

Active Transport:
Active transport is a uphill process why?

• Proteins transport substances from a low concentration to a high concentration (‘uphill’ transport) by using energy
• It is carried out by membrane-proteins.
• Transport rate reaches a maximum when all the protein transporters are being used or are saturated.
• This carrier protein is very specific in transport and sensitive to inhibitors that react with protein side chains.

Comparison of Different Transport Processes:

• Proteins in the membrane show common characteristics of being highly selective; they are liable to saturate, respond to inhibitors and are under hormonal regulation.
• But diffusion whether facilitated or not take place only along a gradient and do not use energy.

Plant- Water relations:

• Water is the medium in which most substances are dissolved.
• The protoplasm of the cell contains water in which different molecules are dissolved and suspended.
• A watermelon has over 92 percent water; most herbaceous plants have only about 10 to 15 percent of its fresh weight as dry matter.
• Terrestrial plants take up huge amount water daily but most of it is lost to the air through evaporation from the leaves, i.e., transpiration.
• A mature corn plant absorbs almost three litres of water in a day, while a mustard plant absorbs water equal to its own weight in about 5 hours.
• Water is the limiting factor for plant growth and productivity.

Water Potential:

• It is the sum of Solute potential and pressure potential.
• • \(\Psi_{w}=\Psi_{x}+\Psi_{p}\)
• Water potential is denoted by the Greek symbol Psi.
• It is expressed in pressure units such as pascals (Pa).

Solution have a lower water potential than pure water why?
When solute dissolves water potential is decreased called solute potential (negative sign)

• Water molecules possess kinetic energy. The greater the concentration of water in a system, the greater is its kinetic energy or ‘water potential’.
• Water move from the higher water potential to the lower water potential.

How can increase water potential?

• If a pressure greater than atmospheric pressure is applied to pure water or a solution, its water potential increases
• Water enters a plant cell due to diffusion causing a pressure built up against the cell wall, it makes the cell turgid, this increases the pressure potential. (sign is positive)
• Water potential of a cell is affected by both solute and pressure potential.

Osmosis:
It is the diffusion of water across the semi-permeable membrane.
Rate of osmosis: It is influenced by

• pressure gradient
• concentration gradient.

1. In plant cells, the cell membrane the membrane of the vacuole (tonoplast) are together determines the movement of molecules in or out of the cell.

2. Water flows from its region of higher chemical potential (or concentration) to its region of lower chemical potential until equilibrium is reached.

3. At equilibrium the two chambers should have the same water potential.

Experiment to demonstrate osmosis:
1. In potato osmometer experiment, the tuber is placed in water the cavity in the potato tuber containing a concentrated solution of sugar collects water due to osmosis.

2. In thistle funnel experiment, sucrose solution in a funnel is separated from pure water in a beaker through a semi-permeable membrane .After some time water will move into the funnel resulting in rise in the level of the solution in the funnel. This will continue till the equilibrium is reached.

Reverse osmosis:
If an external pressure is applied from the upper part of the funnel, no water diffuses into the funnel through the membrane.
1. This pressure required to prevent water from diffusing is the osmotic pressure and this is the function of the solute concentration.

2. If increasing the solute concentration, the greater pressure is required to prevent water from diffusing in. Osmotic pressure is the positive pressure applied, while osmotic potential is negative.

3. A demonstration of osmosis. A thistle funnel is filled with sucrose solution and kept inverted in a beaker containing water, (a) Water will diffuse across the membrane (as shown by arrows) to raise the level of the solution in the funnel (b) Pressure can be applied as shown to stop the water movement into the funnel.

Plasmolysis:
Importance of hypertonic solution:
When a cell is placed in a hypertonic solution water moves out due exosmosis, it causes the protoplast to shrink away from the walls. This is called plasmolysis. The cell become flaccid in state. The process of plamolysis is usually reversible.

Cells become turgid state in pure water?
When the cells are placed in a hypotonic solution (higher water potential or dilute solution as compared to the cytoplasm), water diffuses into the cell due to endosmosis causing the cytoplasm to build up a pressure against the wall, that is called turgor pressure.

Isotonic solution:
If the external solution balances the osmotic pressure of the cytoplasm,it is said to be isotonic. When the cell (or tissue) is placed in an isotonic solution, there is no net flow of water towards the inside or outside. If the external solution is more dilute than the cytoplasm, it is hypotonic, cells swell in hypotonic solutions and shrink in hypertonic ones.

Imbibition:
Imbibition is a special type of diffusion when water is absorbed by hydrophilic colloids and increase in volume.
Examples of imbibition:

1. Absorption of water by seeds and dry wood
2. Emerging out of seedlings from the soil

Water potential gradient between the absorbent and the liquid imbibed is essential for imbibition.

Long distance transport of water:

• Mass flow is the movement of substances in bulk or en masse from one point to another as a result of pressure differences between the two points.
• The bulk movement of substances through the conducting or vascular tissues of plants is called translocation.
• Xylem is associated with translocation of water, mineral salts, some organic nitrogen and hormones, from roots to the aerial parts of the plants.
• Phloem translocates organic and inorganic solutes, mainly from the leaves to other parts of the plants.

How do Plants Absorb Water?
Water is absorbed along with mineral solutes move deeper into root layers by two distinct pathways.
1. Apoplast pathway:

• The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells except at the casparian strips of the endodermis in the roots.
• The apoplast does not provide any barrier to water movement and water movement is through mass flow i.e tension develop in the continuous stream of water in the apoplast due to the adhesive and cohesive properties of water

2. Symplast pathway:

• In symplastic movement the water travels through the cytoplasm of the cells
• This intercellular movement takes place through the plasmodesmata. ‘Symplastic movement is aided by cytoplasmic streaming.
• eg: cytoplasmic streaming in cells of the Hydrilla leaf; the movement of chloroplast due to streaming is easily visible.

Apoplastic pathway is not always continuous through cell wall why?
Apoplastic pathway is continuous upto the inner boundary of the cortex, the endodermis, is impervious,to water because of a band of suberised matrix called the casparian strip.

The water then moves through the symplast and again crosses a membrane to reach the cells of the xylem. This is the only way water and other solutes can enter the vascular cylinder.

Additional structures in water and mineral absorption:
1. A mycorrhiza is a symbiotic association of a fungus with a root system. The hyphae have a very large surface area that absorb mineral ions and water from the soil. The fungus provides minerals and water to the roots, in turn the roots provide sugars and N-containing compounds to the mycorrhizae.

2. Some plants have an obligate association with the mycorrhizae. For example, Pinus seeds cannot germinate and establish without the presence of mycorrhizae.

Water Movement up a Plant:
Root Pressure:

• As various ions from the soil are actively transported into the vascular tissues of the roots, water flows (its potential gradient) and increases the pressure inside the xylem.
• This positive pressure is called root pressure.
• It helps to pushing up water to small heights.

Experiment to demonstrate root pressure:
When a small soft-stemmed plant is taken and cut the stem horizontally near the base with a sharp blade, early in the morning ,the drops of solution ooze out of the cut stem; this occurs due to positive root pressure.

When root pressure is high in herbaceous plants?
Effects of root pressure is also observable at night and early morning when evaporation is low, and excess water collects in the form of droplets around special openings of veins near the tip of grass blades, and leaves of many herbaceous parts.

Such water loss in its liquid phase is known as guttation. Root pressure do not play a major role in water movement up tall trees but it occurs in most plants by transpiratory pull

Transpiration pull:

• Water is mainly ‘pulled’ through the plant with help of driving force – transpiration from the leaves referred to as the cohesion – tension – transpiration pull model of water transport.
• Less than 1 percent of the water reaching the leaves is used in photosynthesis and plant growth.
• Most of it is lost through the stomata in the leaves. This water loss is known as transpiration.

Transpiration:
Transpiration is the evaporative loss of water occurs mainly through the stomata in the leaves.

• Normally stomata are open in the day time and close during the night.
• The opening or closing of the stomata is due to change in the turgidity of the guard cells.
• The inner wall of each guard cell is thick and elastic.
• When turgidity increases within the two guard cells the thin outer walls bulge out and opens the stoma. This is also aided due to the orientation of the microfibrils in the cell walls of the guard cells.
• When the guard cells lose turgor, due to water loss (or water stress) the guard cells become flaccid and the stoma closes.

Distribution of stomata in leaf:

• The dorsiventral (often dicotyledonous) leaf has a greater number of stomata in the lower surface
• Isobilateral (often monocotyledonous) leaf they are equally distributed on both surfaces.

Factors influencing transpiration:
External factors:
Temperature, light, humidity, wind speed

Plant factors:
Number and distribution of stomata, number of stomata open, per cent, water status of the plant, canopy structure, etc.

The transpiration driven ascent of xylem sap depends mainly on the following physical properties of water:

• These properties give water high tensile strength, i.e., an ability to resist a pulling force, and high capillarity, i.e., the ability to rise in thin tubes.
• In plants capillarity is aided by the small diameter of the tracheary elements – the tracheids and vessel elements
• As water evaporates through the stomata results in pulling of water molecule by molecule, into the leaf from the xylem.
• This occurs due to lower concentration of water vapour in the atmosphere as compared to the substomatal cavity and intercellular spaces, water diffuses into the surrounding air. This creates a ‘puli’.

Transpiration and Photosynthesis – a Compromise:
Advantageous of transpiration:

1. creates transpiration pull for absorption and transport of plants
2. supplies water for photosynthesis
3. transports minerals from the soil to all parts of the plant
4. cools leaf surfaces, sometimes 10 to 15 degrees, by evaporative cooling
5. maintains the shape and structure of the plants by keeping cells turgid
6. When water depleted by transpiration, photosynthesis is limited.
7. The evolution of the C₄ photosynthetic system maximising the availability of CO₂ while minimising water loss.
8. C₄ plants are twice as efficient as C₃ plants in terms of fixing carbon (making sugar). C₄ plant loses only half as much water as a C₃ plant for the same amount of CO₂ fixed.

Uptake and transport of mineral nutrients: The nutritional requirements are obtained from minerals in the soil.
Uptake of Mineral Ions:
All minerals cannot be passively absorbed by the roots because

• The active uptake of ions is partly responsible for the water potential gradient in roots, and therefore for the uptake of water by osmosis.
• Specific proteins in the membranes of root hair cells actively pump ions from the soil into the cytoplasm of the epidermal cells.
• Root endodermis because of the layer of suberin has the ability to actively transport ions in one direction only.

Translocation of Mineral Ions:
Chiefsinks:

1. Apical and lateral meristems
2. young leaves
3. developing flowers
4. fruits and seeds
5. the storage organs

Unloading of mineral ions occurs at the fine vein endings through diffusion and active uptake by these cells.

• Some elements that are structural components like calcium are not remobilised.
• An analysis of the xylem exudates shows that though more amount of nitrogen carried in the organic form as amino acids small amounts of P and S are carried as organic compounds.
• Small amount of exchange of materials does take place between xylem and phloem.

Phloem transport: flow from source to sink:
Phloem transport is bidirectional but xylom transport is unidirectional why?
Source is the part of the plant which synthesises the food. Sink is the part that needs or stores the food. Food ( sucrose) is transported by phloem from a source to a sink.lt is the downward transport Sugar stored in roots are mobilized to the buds of trees during early spring and act as sink.

This is called upward transport .Hence phloem transport is bi-directional. Phloem sap is mainly water and sucrose, but other sugars, hormones and amino acids are also transported or translocated through phloem. Xylem transport is always unidirectional, i.e. upwards.

The Pressure Flow or Mass Flow Hypothesis:
The accepted mechanism used for the translocation of sugars from source to sink is called the pressure flow hypothesis.
What is the loading of phloem?
The sugar is moved in the form of sucrose(a disaccharide) into the companion cells and then Tlpo!stem. into the living phloem sieve tube cells by active transport. This process is called loading. It produces a hypertonic condition in the phloem.

• Phloem tissue is composed of sieve tube cells, which form long columns with holes in their end walls called sieve plates. ‘Cytoplasmic strands pass through the holes in the sieve plates,
• Water in the adjacent xylem moves into the phloem by osmosis.
• As hydrostatic pressure( Osmotic pressure) builds up in the in the phloem sieve tube, pressure flow begins and phloem sap move to areas of lower pressure
• Active transport is necessary to move the sucrose out of the phloem sap and sugars are removed, the osmotic pressure decreases and water moves out of the phloem.
• The loss of solute produces a high water potential in the phloem, and water passes out to xylem.

Girdling experiment:
It is used to identify the tissues through which food is transported. On the trunk of a tree a ring of bark up to a depth of the phloem layer is removed. In the absence of downward movement of food ,the portion of the bark above the ring on the stem becomes swollen after a few weeks.

This simple experiment shows that phloem is the tissue responsible for translocation of food and transport takes place in one direction, i.e., towards the roots.

Students can Download Chapter 6 Cell Cycle and Cell Division Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 6 Cell Cycle and Cell Division

Cell cycle:
It involves

1. Cell division
2. DNA replication
3. Cell growth

these all process take place in a coordinated way. The replicated chromosomes (DNA) are then distributed to daughter nuclei.

Phases of Cell Cycle:
Time taken for division:
The duration of cell cycle vary from organism to organism and also from cell type to cell type

• In typical eukaryotic cell cycle (human cells in culture) cells divide once in every 24 hours
• Yeast cell divide in every 90 minutes.

The cell cycle and two basic phases:

• Interphase
• M Phase (Mitosis phase)

Interphase:
The interphase lasts more than 95% of the duration of cell cycle. It is divided into three phases.
1. G1 phase (Gap 1):
G phase is the interval between mitosis and initiation of DNA replication. In this phase cell is metabolically active and continuously grows.

2. S phase (Synthesis):
It is the period which DNA synthesis or replication takes place.

What happens to DNA after S phase?
During S phase amount of DNA per cell doubles. If the initial amount of DNA is denoted as 2C then it Increases to 4C. But the chromosome number is not changed

Events in nucleus and cytoplasm:
In animal cells, during the S phase, DNA replication begins nucleus, and the centriole duplicates in the cytoplasm.

3. G2 phase (Gap 2):
During the G2 phase, proteins are synthesised in preparation for mitosis while cell growth continues.

M Phase (Mitosis phase):

• M Phase represents actual cell division or mitosis
• The M Phase starts with the nuclear division and the separation of daughter chromosomes (karyokinesis).
• It ends with division of cytoplasm (cytokinesis).

Quiescent stage (Go)L
Some cells in the adult animals do not exhibit division (e.g, heart cells), exit G1 phase to enter an inactive stage called quiescent stage.

Common features:
Cells in this stage remain metabolically active but no longer proliferate .But proliferate depending on the requirement of the organism.

M Phase:
This is the most dramatic period of the cell cycle.
Mitosis is an eauational division why?
The number of chromosomes in the parent and progeny cells is the same hence* it is also called as equational division. Mitosis is divided into the following four stages:

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

1. Prophase:
It starts after cthe completion of G2 phase.
Key features:

• Chromosomal material condenses to form compact mitotic chromosomes. It consists of two chromatids attached together at the centromere.
• Initiation of the assembly of mitotic spindle fibres.
• At the end of prophase golgi complexes, endoplasmic reticulum, nucleolus and the nuclear envelope disappears.
• The centriole begins to move towards opposite poles of the cell.

2. Metaphase:
The plane of alignment of the chromosomes at metaphase is referred to as the metaphase plate.
Maximum condensation of chromosome:
In this stage, condensation of chromosomes is completed and morphology of chromosomes can be easily studied. key features:

• Spindle fibres attach to kinetochores of chromosomes.
• Chromosomes are moved to spindle equator and get aligned along metaphase plate through spindle fibres to both poles.

3. Anaphase:
key features:

• Centromeres split and daughter chromatids separate.
• Chromatids move to opposite poles and centromere of each chromosome is towards the pole.

4. Telophase
It is the final stage of mitosis, in which the chromosomes reached their respective poles
key features:

• Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements. Chromosome decondense as chromatin material.
• Nuclear envelope assembles around the chromosome clusters.
• Nucleolus, golgi complex and ER reappears.

Cytokinesis:
In this two daughter cells separate by a process called cytokinesis.
Cytokinesis in animal cell:
In an animal cell, the appearance of a furrow in the plasma membrane which gradually deepens and ultimately joins in the centre, dividing the cell cytoplasm into two.

Cytokinesis in plant cell:
In plant cells, wall formation starts in the centre of the cell and grows outward to meet the lateral walls. The formation of the new cell wall begins with the formation of a simple precursor, called the cell-plate that represents the middle lamella between the walls of two adjacent cells.

How does a cell become multinucleated?
In some organisms karyokinesis is not followed by cytokinesis as a result of which multinucleate condition arises leading to the formation of syncytium (eg: liquid endosperm in coconut).

Significance of Mitosis:
Mitosis is restricted to the diploid cells only. But in some lower plants and in some social insects haploid cells also divide by mitosis.

1. Mitosis results in the production of diploid daughter cells with identical genetic constitution.
2. The growth of multicellular organisms is due to mitosis.
3. Cell growth results in disturbing the ratio between the nucleus and the cytoplasm.
4. Mitosis helps to cell repair, i.e cells of the upper layer of the epidermis, cells of the lining of the gut, and blood cells are being constantly replaced.
5. Mitotic divisions in the meristematic tissues – the apical and the lateral cambium, result in a continuous growth of plants throughout their life.

Meiosis:
The cell division that reduces the chromosome number by half results in the production of haploid daughter cells. This kind of division is called meiosis.

What is common to sexually reproducing organisms?
Meiosis ensures the production of haploid phase in the life cycle of sexually reproducing organisms whereas fertilisation restores the diploid phase.

Key features:

1. Meiosis involves two sequential cycles of nuclear and cell division called meiosis I and meiosis II but only a single cycle of DNA replication.
2. Meiosis I is initiated after the parental chromosomes have replicated to produce identical sister chromatids at the S phase.
3. Meiosis involves pairing of homologous chromosomes and recombination between them.
4. Four haploid cells are formed at the end of meiosis II.

Meiosis I:
Prophase I:
Prophase is typically longer and more complex when compared to prophase of mitosis. It is subdivided into five phases based on chromosomal behaviour i.e., Leptotene, Zygotene, Pachytene, Diploteneand Diakinesis.

Metaphase I:
The bivalent chromosomes align on the equatorial plate. The spindle fibers attach to the pair of homologous chromosomes.

Anaphase I:
The homologous chromosomes separate, while sister chromatids remain associated at their centromeres.

Telophase I:
The nuclear membrane and nucleolus reappear. After cytokinesis diad of cells are formed. The stage between the two meiotic divisions is called interkinesis. It is short lived. Interkinesis is followed by prophase II, a much simpler prophase than prophase I.

Meiosis II:
Meiosis II resembles a normal mitosis

Prophase II:
Meiosis II begins after cytokinesis, The nuclear membrane disappears by the end of prophase II. The chromosomes again become compact.

Metaphase II:
At this stage the chromosomes align at the equator and Spindle fibers get attached to the kinetochores of sister chromatids.

Anaphase II:
It begins with splitting of the centromere of each chromosome allowing them to move toward opposite poles of the cell.

Telophase II:
Meiosis ends with telophase II, in which the two groups of chromosomes get enclosed by a nuclear envelope; cytokinesis follows resulting in the formation of tetrad of cells i.e., four haploid daughter cells.

Significance of meiosis:

Students can Download Chapter 5 Cell The Unit of Life Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 5 Cell The Unit of Life

What is a cell?
Cell is the structural and functional unit of all living organisms. Anton Von Leeuwenhoek first saw and described a living cell Robert Brown discovered the nucleus Unicellular organisms are capable of

• independent existence and
• performing the essential functions of life.

Cell theory:
Schleiden and Schwann together formulated the cell theory:

• In 1838, Malthias Schleiden, a German botanist proposed that all plants are composed of different kinds of cells.
• In 1839 Schwannan British Zoologist, studied different types of animal cells and reported plasma membrane.

Rudolf Virchowd 855) -Contribution of modification of cell theory:
The new cells arise from pre-existing cells (Omnis cellula-e cellula)
Core elements of cell theory:

An overview of cell:
Cell boundary of plant cell and animal cell:

• The onion cell which is a typical plant cell, has a distinct cell wall and inner cell membrane.
• The cells of the human cheek have an outer membrane as the delimiting structure of the cell.

Prokaryotic and eukaryotic cell body:

• Cells that have membrane bound nuclei are called eukaryotic whereas cells that lack a membrane bound nucleus are prokaryotic.
• In both prokaryotic and eukaryotic cells, a semi-fluid matrix forms the cytoplasm.

Membrane bound cell organelle of eukaryotes:

1. Nucleus
2. Endoplasmic reticulum (ER)
3. Golgi complex
4. Lysosomes
5. Mitochondria
6. Microbodies
7. Vacuoles.

Which is the common cell organelle found in both prokaryotes and eukaryotes?
Ribosomes are non-membrane bound organelles found in both eukaryotic and prokaryotic cell.

• Ribosomes are found not only in the cytoplasm but also within the organelles – chloroplasts and mitochondria and on rough ER.
• Animal cells contain another non-membrane bound organelle called centriole which helps in cell division.

Cells in different measurement:

The largest cell is the egg of an ostrich and the longest is Nerve cells.

Prokaryotic cells:
The prokaryotic cells are represented by {bacteria, blue-green algae, mycoplasma and PPLO (Pleuro Pneumonia Like Organisms)}
Classification based on the shape:

1. Bacillus (rod like)
2. Coccus (spherical
3. Vibrium (comma shaped)
4. Spirillum (spiral)

(a) The fluid matrix found in the prokaryotic cell is the cytoplasm.

(b) There is no well-defined nucleus

Plasmids:
In addition to the genomic DNA, many bacteria have small circular DNA outside the genomic DNA. These are called plasmids .So they are organisms resistance to antibiotics. The invaginations of plasma membrane seen inside the cell is called mesosome

Cell Envelope and its Modifications:
Three layers of Cell boundary:

1. Glycocalyx (Outer)
2. The cell wall (Middle)
3. Plasma membrane (Inner)

(a) In some bacteria, Glycocalyx is a loose sheath called the slime layer while in others it is thick and tough, called the capsule

(b) Cell wall determines the shape of the cell and provides a strong structural support to prevent the bacterium from bursting.

Mesosome:
They are the extensions of plasma membrane in the form of vesicles, tubules and lamellae.

Functions
They help in

1. cell wall formation 1
2. DNA replication, distribution.to daughter cells
3. respiration
4. secretion processes
5. increase the surface area of the plasma membrane.

Chromatophores:
Membranous extensions in the cytoplasm which contain pigments. eg: cyanobacteria

Three parts of bacterial flagellum

1. Filament
2. Hhook
3. Basal body.

The other important surface structures in bacteria:

1. The pili are elongated tubular structures helps in conjugation
2. The fimbriae are small bristle like fibres helps to attach the bacteria on rocks in streams and the host tissues.

Gram +ve and gram -ve:
Christian Gram introduced this method for classifying bacteria. Bacteria that can retain stain(crystal violet) are called Gram positive Bacteria that cannot retain stain are called Gram negative.

Ribosomes and inclusion Bodies:

• In prokaryotes 70S prokaryotic ribosomes consists of subunits – 50S and 30S units.
• Several ribosomes attach to a single mRNA and form a chain called polyribosomes or polysome.

Function:
The ribosomes translate the mRNA into proteins.

Inclusion bodies:

• The examples are phosphate granules, cyanophycean granules and glycogen granules.
• Gas vacuoles are found in blue green and purple and green photosynthetic bacteria.

Eukaryotic cells
They possess well defined and membrance bound cell organelles include

1. protists
2. plants
3. animals
4. fungi.

Cell Membrane:
Structure of membrane:

• It consist of lipid bilayer arranged within the membrane with the polar head towards the outer sides and the hydrophobic tails towards the inner part.
• The non polar tail of saturated hydrocarbons is protected from the aqueous environment
• The ratio of protein and lipid varies in different cell types.
• In human beings, the membrane of the erythrocyte has approximately 52 per cent protein and 40 per cent lipids
• The peripheral proteins lie on the surface of membrane while the integral proteins are buried in the membrane.

Who proposed the well accepted model of membrane?
Singer and Nicolson (1972) proposed the fluid mosaic model.The quasi-fluid nature of lipid enables lateral movement of proteins within the bilayer.
Functions:

1. Transport molecules without energy requirement called as passive transport
2. Neutral solutes move across the membrane from higher concentration to the lower by the process of simple diffusion.
3. Water move across this membrane from higher to lower concentration by diffusion is called osmosis.

Carrier protein in transport:
As the polar molecules cannot pass through the non polar lipid bilayer, they require a carrier protein to facilitate their transport across the membrane.

Carrier protein and energy in transport:
A few ions or molecules are transported across the membrane from lower to the higher concentration with the help of energy (ATP is utilized). It is called active transport eg: Na⁺/K⁺ Pump.

Cell Wall:
Function:
Cell wall gives shape and protects the cell from mechanical damage and infection. It also helps in cell-to-cell interaction and provides barrier to undesirable macromolecules.

Algal cell wall:
It consists Cellulose, galactans, mannans and minerals like calcium carbonate.

Plant cell wall:
It consists of cellulose, hemicellulose, pectins and proteins.

• The cell wall of a young plant cell, the primary wall is capable of growth, which later disappears and secondary wall is formed on the inner (towards membrane) side of the cell
• The middle lamella is made up of calcium pectate which holds the neighbouring cells together.
• Cytoplasmic strands like plasmodesmata which connects cytoplasm of one cell to another through cell wall and middle lamellae.

Endomembrane System:
The endomembrane system include

1. endoplasmic reticulum (ER)
2. golgicomplex
3. lysosomes
4. vacuoles.

1. The Endoplasmic Reticulum (ER):
Salient features:

• It is the network of tubular structures scattered in the cytoplasm
• ER divides the intracellular space into two distinct compartments, i.e., luminal(inside ER) and extra luminal (cytoplasm)compartments.

Rough endoplasmic reticulum and Smooth endoplasmic reticulum:
The endoplasmic reticulum bearing ribosomes on their surface is called rough endoplasmic reticulum (RER). It is involved in protein synthesis and secretion.

The endoplasmic reticulum devoid of ribosome are called smooth endoplasmic reticulum (SER). It is involved in synthesis of lipids In animal cells, lipid-like steroidal hormones are synthesised

2. Golgi apparatus:
It was first observed Camillo Golgi (1898) as densely stained reticular structures near the nucleus.
Function:

• Packaging of materials
• It is the important site of formation of glycoproteins and glycolipids.

Salient features:

• They consist of many flat, disc-shaped sacs or cisternae of 0.5 μm to 1.0 μm diameter stacked parallel to each other
• The Golgi cisternae are concentrically arranged near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face. The cis and the trans faces are interconnected.
• Materials to be packaged in the form of vesicles from the ER fuse with the cis face of the golgi apparatus and move towards the maturing face.
• The proteins arise from the endoplasmic reticulum are modified in the cisternae of the golgi apparatus and are released from its trans face.

3. Lysosomes:
Salient features:

• * They are membrane bound vesicular structures formed by the process of packaging in the golgi apparatus.
• The hydrolytic enzymes found in these vescicles (hydrolases – lipases, proteases, carbohydrases) are active at the acidic pH.
• These enzymes are capable of digesting carbohydrates, proteins, lipids and nucleic acids.

4. Vacuoles:
Salient features:

• It is the membrane-bound space found in the cytoplasm.
• It contains water, sap, excretory product and other materials
• In plant cells the vacuoles occupy up to 90 percent of the volume of the cell.
• The membrane surrounding the vacuole is the tonoplast,

Function:
It facilitates the transport of ions and other materials against concentration gradients into the vacuole

Type of vacuoles in lower organisms:
In Amoeba the contractile vacuole is important for excretion. In protists, food vacuoles are formed by engulfing the food particles.

Mitochondria:
Salient features:

1. It is the cylindrical structure having a diameter of 0.2 to 1.0μm
2. Each mitochodrion is a double membrane bomd structure.
3. The inner compartment is called matrix
4. The outer membfrane forms the continous limiting boundary of the oraganelle
5. The inner membrane forms a number of infoldings called the cristae that uncreases surface area.
6. The matrix possess single circular DNA molecule, a few RNA molecules, and ribosomes(70s)
7. The mitochondria divide by fission.

Function:
Mitochondria are the sites of aerobic respiration.

Power house of a cell:
They produce cellular energy in the form of ATP, hence they are called ‘power houses’ of the cell.

Plastids:
Plastids are found in all plant cells and in euglenoids.
Classification of plastids based on the type of pigments:
1. Chloroplasts:
The chloroplasts contain chlorophyll and carotenoid pigments which are responsible for trapping light energy essential for photosynthesis.

2. Chromoplasts:
In the chromoplasts, fat soluble carotenoid pigments like carotene and xanthophylls are present

3. Leucoplasts:
The leucoplasts are the colourless plastids of varied shapes and sizes with stored nutrients:

Classification of leucoplast:

Chloroplast:
It is found in the mesophyll cells of the leaves. These are lens-shaped,oval, spherical, discoid or even ribbon-like organelles having variable length.

Structure of chloroplast:

• Chloroplasts are also double membrane bound.
• The space limited by the inner membrane of the chloroplast is called the stroma.
• The stroma contains enzymes required for the synthesis of carbohydrates and proteins.
• It also contains small, double-stranded circular DNA molecules and ribosomes(70S).
• A number of organised flattened membranous sacs called the thylakoids (Chlorophyll pigments seen) are present in the stroma These are arranged in stacks like the piles of coins called grana.
• Stroma lamellae connecting the thylakoids of the different grana.

Ribosomes:
These are granular structures first observed under the electron microscope as dense particles by George Palade(1953).
Chemical composition:
They are composed of ribonucleic acid (RNA) and proteins

Salient features:

• The eukaryotic ribosomes are 80S. Here ‘S’ stands for the sedimentation coefficient
• It consists of two sub units 60S and 40S.
• It translate coded information in mRNA into protiens

Cytoskeleton:
Salient features:
These are network of filamentous proteinaceous structures present in the cytoplasm
Function:

1. Mechanical support
2. Motility
3. Maintenance of the cell shape.

Cilia and Flagella:
Salient features:

• Cilia and flagella are hair-like outgrowths of the cell membrane..
• Flagella are longer and responsible for cell movement.
• Their core is called the axoneme, possesses a number of microtubules running parallel to the long axis
• The axoneme has nine pairs of doublets of radially arranged peripheral microtubules, and a pair of centrally located microtubules.Such an arrangement is 9 + 2.

Centrosome and Centrioles:
Salient features:

• Centrosome is an organelle containing two cylindrical structures called centrioles
• Both the centrioles in a centrosome lie perpendicular to each other.
• It has cartwheel like organisation and made up of nine peripheral triplet fibrils of tubulin.
• The central part of the centriole is also proteinaceous and called the hub, which is connected with tubules of the peripheral triplets by radial spokes.

Function:
The centrioles form the basal body of cilia or flagella and spindle fibres (give rise to spindle apparatus during cell division in animal cells)

Nucleus:
It was first described by Robert Brown in 1831. Nucleus stained by the basic dyes was given the name chromatin by Flemming

Non nucleated plant and animal cells:

• Erythrocytes of many mammals
• Sieve tube cells of vascular plants

Components of nucleus:

1. nucleoplasm
2. chromatin
3. nuclear matrix
4. nucleoli.

Salient Features:

• The outer membrane is continuous with endoplasmic reticulum and bears ribosomes on it.
• These nuclear pores are the passages through which RNA and protein molecules moves.
• The space between two membrane is called the perinuclear space(10 to 50 nm). The nuclear matrix or the nucleoplasm contains nucleolus and chromatin.
• The nucleoli are spherical structures (site for active ribosomal RNA synthesis).
• Larger and numerous nucleoli are present in cells actively carrying out protein synthesis.
• During cell division chromatin condensed to form chromosomes.

Components of chromosome:

1. DNA
2. basic proteins(histones)
3. non-histone proteins
4. RNA.

Parts of chromosome:
It has primary constriction or the centromere on the sides of which disc shaped structures called kinetochores. A few chromosomes have non-staining secondary constrictions that possess knob like structure called satellite.

Classification of chromosome based on position of centromere:

1. Metacentric chromosome has middle centromere forming two equal arms.
2. Sub-metacentric chromosome has centromere nearer to one end of the chromosome so it has shorter arm and one longer arm.
3. In acrocentric chromosome the centromere is situated close to its end so it has one extremely short and one very long arm.
4. Telocentric chromosome has a terminal centromere.

Microbodies:
It is the membrane bound vesicles called microbodies (contain various enzymes) are present in both plant and animal cells.

Students can Download Chapter 4 Anatomy of Flowering Plants Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 4 Anatomy of Flowering Plants

What is plant anatomy?
It is the study of internal structure of plants. In angiosperms, the monocots and dicots are anatomically different.

The Tissues:
Group of cells having a common origin and function.
Do you agree that all tissue in plants are capable of division?
Some tissues are capable of division they are called meristemetic tissues, while others are capable of divisor , they are called permanent tissues.

Meristemetic Tissue:
They are found in specific region of plant i.e. growing region the tips of roots and shoots
Classification based on the position:

1. Apical meristem
2. Inter calary meristem
3. Lateral meristem.

1. Apical meristem:
In root it is situated at the tip while in shoot it lies in the distant most region of the stem axis. The portion of shoot apical meristem i.e axillary bud present in the axils of leaves forms branch or a flower.

2. Intercalary meristem:
It occurs between mature tissues or base of internode of grasses. The above two meristems are primary meristems because they appear early in the life of a plant.

Grasses in an area are cut and removed by cows, after few days regeneration occurs and new grasses are formed. Why?
Due to the activity of intercalary meristem.

3. Secondary or lateral meristem:
It occurs in the mature regions of roots and shoots of plants particularly in woody axis. Eg-Fascicular vascular cambium, interfascicular cambium and cork-cambium.

For example: In some woody species after few years thickness of plant body increases from 5 inch diameter to 10 inch diameter. Why this happens?
Due to the activity of lateral meristem

What is permanent tissues?
Meristems structurally and functionally specialised and lose the ability to divide. Such cells are termed as permanent tissues.

Permanent Tissues:
Classification:

• Simple tissues: They are made up of similar kind of cells
• Complex tissues: They are made up of different kind of cells

Simple Tissue:
1. Parenchyma:

• They are isodiametric, spherical, oval, round, polygonal or elongated in shape.
• Their walls are thin and made up of cellulose.
• They may either be closely packed or have small intercellular spaces.

Functions:
Photosynthesis, storage and secretion.

2. Collenchyma:

• It occurs just below the epidermal layer.
• Cells of this tissue are thickened at the corners due to a deposition of cellulose, hemicellulose and pectin.
• Collenchymatous ceils may be oval, spherical or polygonal and contain chloroplasts.
• Intercellular spaces are absent.

Function:
Mechanical support.

3. Sclerenchyma:

• They are thick, dead and lignified with few or numerous pits.
• They are classified into fibres and sclereids.
• The fibres are thick-walled, elongated and pointed cells occuring in groups.

Function:
Mechanical support to organs.

Structure and position of sclereids in plants:
They are spherical, oval or cylindrical, highly thickened dead cells with very narrow cavities (lumen). These are found in the fruit walls of nuts; pulp of fruits like guava, pear and sapota; seed coats of legumes and leaves of tea.

Complex Tissues:
Xylem and phloem are considered as complex tissues in plants
Xylem:

• It conducts water and minerals from roots to the stem and leaves.
• It also provides mechanical strength to the plant parts.
• Gymnosperms lack vessels in their xylem.
• It is composed of four different kinds of elements

Tracheids, vessels, xylem fibres and xylem parenchyma.
1. Tracheids:
They are dead and without protoplasm.They are elongated or tube like cells with thick and lignified walls and tapering ends. In flowering plants, tracheids and vessels are the main water transporting elements.

2. Vessel:
It is a long cylindrical tube-like structure having lignified walls and a large central cavity. They are devoid of protoplasm and interconnected by perforations in their common walls. The presence of vessels is a characteristic feature of angiosperms.

3. Xylem fibres:
They have highly thickened walls and are dead. These may either be septate or aseptate.

4. Xylem parenchyma”

• They are cellulosic, living and thin-walled.
• They store food materials in the form of starch or fat, and other substances like tannins.
• Radial conduction of water takes place by the ray parenchymatous cells.
• Primary xylem is of two types – protoxylem and metaxylem. The first formed primary xylem elements are called protoxylem and the later formed primary xylem is called metaxylem.

Difference between endarch and exarch condition:
In stems, the protoxylem lies towards the centre (pith) and the metaxylem lies towards the periphery of the organ. It is called endarch. In roots, the protoxylem lies towards periphery and metaxylem lies towards the centre.lt is called exarch.

Phloem:
It transports food materials, usually from leaves to other parts of the plant. Phloem in angiosperms is composed of

Gymnosperms have albuminous cells and sieve cells. They lack sieve tubes and companion cells.
1. Sieve tube elements:

• They are also long, tube-like structures.
• Their end walls are perforated to form the sieve plates.
• A mature sieve element have a large vacuole but lacks a nucleus.
• The functions of sieve tubes are controlled by the nucleus of companion cells.

2. Companion cells:

• They are parenchymatous cells closely associated with sieve tube elements.
• The sieve tube elements and companion cells are connected by pit fields.
• The companion cells help in maintaining the pressure gradient in the sieve tubes.

3. Phloem Parenchyma:

• It consist of cylindrical cells with dense cytoplasm and nucleus.
• The cell wall is composed of cellulose and has pits through which plasmodesmata passes.
• The phloem parenchyma stores food material and other substances like resins, latex and mucilage. Phloem parenchyma is absent in monocots.

4. Phloem fibres (bast fibres):

• They are elongated, unbranched, needle like sclerenchymatous cells.
• At maturity, these fibres lose their protoplasm and become dead.
• These are generally absent in the primary phloem but are found in the secondary phloem.

The Tissue System:
Based on the of their structure and location, there are three types of tissue systems.

1. Epidermal tissue system
2. The ground or fundamental tissue system
3. Vascular or conducting tissue system.

1. Epidermal tissue system:
Stomata are present in the epidermis of leaves regulate the process of transpiration and gaseous exchange.
Shape of guard cell in dicot and monocot:
In dicot, it consist of two bean-shaped cells known as guard cells. In grasses(monocot), the guard cells are dumb bell shaped.

• The outer walls of guard cells are thin and the inner walls are thickened.
• The guard cells possess chloroplasts and regulate the opening and closing of stomata.
• Guard cells are surrounded by specialised cells they are known as subsidiary cells.

What is stomatal apparatus?
The stomatal aperture, guard cells and the surrounding subsidiary cells are together called stomatal apparatus.

• The root hairs help to absorb water and minerals from the soil.
• On the stem the epidermal hairs are called trichomes.
• They have secretory function.
• The trichomes also help to prevent water loss due to transpiration.

2. The Ground Tissue System:

• It includes parenchyma, collenchyma and sclerenchyma.
• Parenchymatous cells are usually present in cortex, pericycle, pith and medullary rays in the primary stems and roots.
• In leaves, the ground tissues are thin-walled chloroplast containing cells called mesophyll.

3. The Vascular Tissue System:
The vascular system consists of phloem and xylem.

Different type bundles:
1. Open vascular bundles:
In dicot stems, Cambium is’present between phloem and xylem.

2. Closed vascular bundle:
In the monocot, the vascular bundles have no cambium present in them. Hence they do not form secondary tissues .

3. Radial bundle:
In roots, xylem and phloem are arranged in an alternate manner on different radii.

4. Conjoint bundle:
In stems and leaves, the xylem and phloem are situated at the same radius of vascular bundles. In this phloem located on the outer side of xylem.

Anatomy Of Dicotyledonous And Monocotyledonous Plants:
Dicotyledonous Root (eg sunflower root):
Salient features:

• The outermost layer is epidermis which is unicellular in root hairs.
• Lower layer is cortex consists of parenchyma cells with intercellular spaces.
• The innermost layer of the cortex is called endodermis.
• It comprises a single layer of barrel-shaped cells without any intercellular spaces

Chemical substance in endodermal wall:

• Its tangential and radial walls have a deposition of water impermeable waxy material-suberin-in the form of casparian strips.
• Next to endodermis is thick walled pericycle. From thisjateral roots and vascular cambium during the secondary growth originates.
• The pith is small.
• Conjuctive tissues are the parenchymatous cells which lie between the xylem and phloem
• Usually two to four xylem and phloem patches. Later, a cambium ring develops between the xylem and phloem.
• Stele is the tissues on the inner side of the endodermis such as pericycle, vascular bundles and pith.

Monocotyledonous Root:
The anatomy of the monocot root is similar to the dicot root in many respects.
Some specialities are given below:

• It has more than six (polyarch) xylem bundles .
• Pith is large and well developed.

Secondary thickening is most common in dicot plants:
Cambium is present only in dicot plant, it is absent in monocots, so Monocotyledonous roots do not undergo any secondary growth.

Dicotyledonous Stem:
Salient features:

1. The outermost protective layer of the stem is epidermis.lt is covered by a thin layer of cuticle.
2. Epidermis consist of trichomes and stomata.
3. Cortex lie between epidermis and pericycle. It consists of outer hypodermis, having collenchymatous cells which provide mechanical strength.
4. Thin walled parenchymatous cells seen below hypodermis.
5. The innermost layer of the cortex is called the endodermis. It consists of starch grains called as the starch sheath. Inner to endodermis is Pericycle.
6. Vascular bundles are arranged in ring It consist of xylem and phloem. Cambium lie between these two.
7. Semi-lunar patches of sclerenchyma occur at the outer part of the phloem.
8. Vascular bundle is conjoint, open, and endarch.
9. Pith is seen at the central part of the stem.

Monocotyledonous Stem Salient features:

• It consist of sclerenchymatous hypodermis and large number of scattered vascular bundles.
• It is surrounded by a sclerenchymatous bundle sheath
• Vascular bundles are conjoint and closed.
• Peripheral vascular bundles are smaller than centrally located ones.
• The phloem parenchyma is absent and water- containing cavities are present within the vascular bundles.

Dorsiventral (Dicotyledonous) Leaf:
Salient features:

• The dorsiventral leaf shows three main parts, namely, epidermis- upper syrface (adaxial epidermis) and lower surface (abaxial epidermis -bears more stomata),
• Mesophyll.- possesses chloroplasts (It has two types of cells palisade parenchyma and spongy parenchyma) and vascular system.
• Vascular system is seen in midrib & viens.
• The vascular bundles are surrounded by a layer of thick walled bundle sheath cells.
• The veins vary in thickness in the reticulate venation of the dicot leaves.

Isobilateral (Monocotyledonous) Leaf:
The vertical section of isobilateral leaf is similar to that of the dorsiventral leaf It shows some differences.
Salient features:

1. It has stomata on both the surfaces of the epidermis
2. Mesophyll is not differentiated into palisade and spongy parenchyma.
3. The position and function of Bulliform cells: In grasses, upper epidermal cells have specialised colourless cells .they are called bulliform cells. It helps in rolling and unrolling of lamina. When they are flaccid due to water stress, they make the leaves curl inwards to minimise water loss. .
4. Venation in monocot leaves is parallel.

Secondary Growth:
What you mean by secondary growth?
Dicotyledonous plants shows secondary growth .i.e it increases the girth of plant body. The tissues involved in secondary growth are lateral meristems eg: vascular cambium and cork cambium

Vascular Cambium:
It is seen in between xylem and pholem. it forms a complete ring.

Formation of cambial ring:
Intra fascicular and inter fascicular cambium- Difference:
In dicot stems, cambium present between primary xylem and primary phloem is the intrafascicular cambium. The medullary cells seen in between xylem & phloem become meristematic and forms interfascicular cambium. Thus, a continuous ring of cambium is formed.

Activity of the cambial ring:
The cambial ring cut off new cells towards the inner (secondary xylem) and the outer sides( secondary phloem).

How can you analyse Canbium is more active towards inner side than outer side?
The cambium is more active on the inner side than on the outer, as a result amount of secondary xylem produced is more than secondary phloem. The primary and secondary phloems get gradually crushed due to the continued formation and accumulation of secondary xylem.

At some places, the cambium forms a narrow band of parenchyma, which passes through the secondary xylem and the secondary phloem are called the secondary medullary rays.

Spring wood and autumn wood:
Spring wood or early wood:
In the spring season, cambium is very active and produces a large number of xylem elements having vessels with wider cavities.This wood is called spring wood.

Autumn wood or late wood:
In winter, the cambium is less active and forms fewer xylem elements that have narrow vessels, This wood is called autumn wood. The spring wood is lighter and autumn wood is darker.

Annual ring in the calculation of age of tree:
The spring wood and autumn wood that appear as alternate concentric rings, constitute an annual ring. Age of tree can be calculate by counting the number of annual rings.

Heartwood – Durable wood?
1. The inner most layers of the stem consist of secondary xylem is dark brown due to deposition of organic compounds like tannins, resins, oils, gums, aromatic substances and essential oils.

2. It is resistant to the attack of microorganisms. This type of wood is called heartwood.

Sap wood:
The outer part of wood is light coloured, functional and and conduct water and minerals . This type of wood is called sap wood.

Cork Cambium:
Due to the activity of vascular cambium, girth of the stem increases. This results the breakdown of outer cortical and epidermis layers .So the new protective tissues are formed by another meristematic tissue called cork cambium or phellogen
Activity of cort cambium & phellogen:
Phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem while the inner cells differentiate into secondary cortex or phelloderm.

Feature of secondary tissues of phellogen and constituents of Periderm:
The cork is impervious to water due to suberin deposition in the cell wall. The cells of secondary cortex are parenchymatous. Phellogen, phellem, and phelloderm are together known as periderm.

Bark:
It is found exterior to the vascular cambium, including secondary phloem. Bark that is formed early in the season is called early or soft bark. Towards the end of the season late or hard bark is formed.

Lenticels and function:
At certain regions, the phellogen cut off closely arranged parenchymatous cells on the outer side instead of cork cells. These cells rupture the epidermis, and forms openings called lenticels. It helps in the exchange of gases between the outer atmosphere and the internal tissue of the stem.

Secondary Growth in Roots:
Can you think of formation of vascular cambium is completely secondary in origin?
In the dicot root, the vascular cambium is completely secondary in origin. lt occurs in the later stages of growth. It originates from the tissue located just below the phloem bundles and a portion of pericycle tissue, opposite to protoxylem forming a complete and continuous wavy ring, which later becomes circular.

Secondary growth also occurs in stems and roots ofgymnosperms. But secondary growth does not occur in monocotyledons.

Students can Download Chapter 2 Plant Kingdom Notes, Plus One Botany Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Botany Notes Chapter 2 Plant Kingdom

Different Plant Groups:

1. Algae
2. Bryophytes
3. Pteridophytes
4. Gymnosperms
5. Angiosperms.

Types of classification:
1. Artificial system of classification:
The systems of classification based morphological characters such as habit, colour, number and shape of leaves, etc i.e based on vegetative characters or on the androecium structure. eg: Linnaeus classification.

2. Natural system of classification:
The systems of classification based on not only the external features, but also internal features, like ultrastructure, anatomy, embryology and phytochemistry. eg: George Bentham and Joseph Dalton Hookers classification

3. Phylogenetic system of classification:
The systems of classification based on evolutionary relationships between the various organisms. eg: Englerand prantl.

Taxonomy in modern approach:
1. Numerical Taxonomy
In this, number and codes are assigned to all the characters and the data are processed. This is carried out using computers based on all observable characteristics.

2. Cytotaxonomy:
In this cytological information like chromosome number, structure and behavior are considered.

3. Chemotaxonomy:
It is based on chemical constituents of the plant.

1. Algae:
Characterestic features:
Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (both fresh water and marine) organisms.

Size of algal forms:

1. Microscopic unicellular forms eg Chlamydomonas,
2. Colonial forms eg Volvox
3. Filamentous forms eg Ulothrix and Spirogyra.

Reproduction:
1. Vegetative reproduction:
It occures by fragmentation. Each fragment develops into a thallus. .

2. Asexual reproduction:
lt occures by the production zoospores. They are flagellated (motile) and on germination gives rise to new plants.

3. Sexual reproduction:
It takes place through fusion of two gametes.

(A) Isogamous:
These gametes are flagellated and similar in size (as in Chlamydomonas) or non-flagellated (non-motile) but similar in size (as in Spirogyra).

(B) Anisogamous:
It is the fusion of two gametes dissimilar in size. eg: species of Chlamydomonas

(C) Oogamous:
It is the fusion between one large, non-motile (static) female gamete and a smaller, motile male gamete eg: Volvox, Fucus.

Economic imoportance:

1. Half of the total carbon dioxide fixation on earth is carried out by algae through photosynthesis.
2. Many species of Porphyra, Laminaria and Sargassum are among the 70 species of marine algae used as food.
3. Certain marine brown and red algae produce large amounts of hydrocolloids (water holding substances), eg: algin (brown algae) and carrageen (red algae) are used commercially.
4. Agar obtained from Gelidium and Gracilaria are used to grow microbes and in preparations of ice-creams and jellies.
5. Chlorella and Spirullina are unicellular algae, rich in proteins and are used as food by space travellers.

Three main classes of algae:

Chlorophyceae (Green algae):
Salient features:

1. The plant body may be unicellular, colonial or filamentous. The dominant green pigments are chlorophyll a and b.
2. The chloroplasts may be discoid, plate-like, reticulate, cup-shaped, spiral or ribbon-shaped in different species.
3. The storage bodies called pyrenoids located in the chloroplasts. Pyrenoids contain protein besides starch.
4. Green algae have a rigid cell wall made of an inner layer of cellulose and an outer layer of pectose.
5. Vegetative reproduction usually takes place by fragmentation.
6. Asexual reproduction is by flagellated zoospores produced in zoosporangia.
7. The sexual reproduction may be isogamous, anisogamous or oogamous.

eg: Chlamydomonas, Volvox, Ulothrix, Spirogyra and Chara.

Phaeophyceae (Brown algae):
Salient features:

1. They are mainly found in marine habitats.
2. The size of plant body range from simple branched, filamentous forms (l=ctocarpus) to profusely branched forms such as kelDs (height 100 metres).
3. They possess chlorophyll a, c, carotenoids and xanthophylls. Fucoxanthin is present in large amount.
4. Food is stored as complex carbohydrates in the form of laminarin or mannitol.
5. The vegetative cells with cellulosic wall is covered on the outside by a gelatinous coating of algin.
6. The plant body is attached to the substratum by a holdfast, and has a stalk, the stipe and leaf like photosynthetic organ-the frond.
7. Vegetative reproduction takes place by fragmentation.
8. Asexual reproduction is by biflagellate zoospores that are pear-shaped and have tyvo unequal laterally attached flagella.
9. Sexual reproduction may be isogamous, anisogamous or oogamous.
10. The gametes are pyriform (pear-shaped) and bear two laterally attached flagella.

eg: Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus.

Rhodophyceae(Red algae):
Salient features:

1. Majority are marine and found in the warmer areas.
2. The red thalli of most of the red algae are multicellular. The chlorophyll pigments are chi a,chi d.
3. The dominant red pigment is r-phycoerythrin.
4. The food is stored as floridean starch similar to amylopectin and glycogen in structure.
5. The red algae usually reproduce vegetatively by fragmentation.
6. They reproduce asexually by non-motile spores and sexually by non-motile gametes.
7. Sexual reproduction is oogamous and accompanied by complex post fertilisation developments.

eg: Polysiphonia, Porphyra, Gracilaria and Gelidium.

2. Bryophytes:
Amphibians of the plant kingdom?
Because these plants are found in damp, humid and shaded localities and dependent on water for sexual reproduction.
Salient features:

• Thallus is prostrate or erect, and attached to the substratum by unicellular or multicellular rhizoids.
• They lack true roots, stem or leaves.
• The main plant body of the bryophyte is haploid. It produces gametes, hence is called a gametophyte.
• The male sex organ is multicellular antheridium. They produce biflagellate antherozoids.
• The female sex organ called archegonium it is flask-shaped and produces a single egg.

Sexual reproduction:
Antherozoid moves through water they come in contact with archegonium and fuses with the egg to produce the zygote. Zygotes produce a multicellular body called a sporophyte.

What is the nature and development of sporophytes of bryophytes?
The sporophyte is not free-living but attached to the photosynthetic gametophyte Some cells of the sporophyte undergo reduction division (meiosis) to produce haploid spores. These spores germinate to produce gametophyte.

Economic importance:

1. They play an important role in plant succession on bare rocks/soil. They decompose rocks making the substrate suitable for the growth of higher plants.
2. Some mosses provide food for herbaceous mammals, birds and other animals.
3. Sphagnum, a moss, provide peat that is used as fuel, and because of their capacity to hold water as packing material for trans-shipment of living material.
4. Mosses form dense mats on the soil hence it prevents soil erosion.

The bryophytes are divided into liverworts and mosses.
Liverworts:
Growing locality:
The liverworts grow in moist, shady habitats such as banks of streams, marshy ground, damp soil, bark of trees and deep in the woods.

What is nature of plant body?
The plant body of a liverwort is thalloid, eg: Marchantia.

Features of Gemmae and its development:
Gemmae are green, multicellular, asexual buds. It is detached from the parent body and germinate to form new individuals.

Structure of sporophvte and spore development:
The sporophyte is differentiated into a foot, seta and capsule. After meiosis, spores are produced within the capsule. These spores germinate to form free-living gametophytes.

Mosses:
Spore germination and protonema:
In the life cycle of bryophytes, spore germinate and forms a creeping, green, branched and a filamentous stage called protonema. The second stage is the leafy stage, which develops from the secondary protonema as a lateral bud.

Features of leafy stage:
They consists of spirally arranged leaves and multicellular branched rhizoids. This stage bears the sex organs. It is the true gametophyte.

Vegetative reproduction:
It takes place by fragmentation and budding in the secondary protonema.

Sexual reproduction.
In sexual reproduction, the sex organs are antheridia and archegonia. After fertilisation, the zygote develops into a sporophyte, consisting of a foot, seta and capsule.

Which group of brvophvte shows well developed sporophyte?
The sporophyte in mosses is more elaborate than that in liverworts. The mosses have an elaborate mechanism of spore dispersal. eg: Funaria, Polytrichum and Sphagnum

3. Pteridophytes:
Salient features:

1. The Pteridophytes are the first terrestrial plants that possess vascular tissues – xylem and phloem. This group includes horsetails and ferns.
2. They are frequently grown as ornamentals.
3. The pteridophytes are found in cool, damp, shady places and require water for fertilisation .
4. The main plant body is a sporophyte which is differentiated into true root, stem and leaves .
5. The leaves in pteridophyta are small (microphylls) as in Selaginella or large (macrophylls) as in ferns.
6. The sporophytes bear sporangia by leaf-like appendages called sporophylls.
7. In some cases sporophylls forms distinct compact structures called strobili or cones (Selaginella, Equisetum).
8. The sporangia produce spores by meiosis in spore mother cells.
9. The spores germinate to give rise multicellular, free-living, photosynthetic thalloid gametophytes called prothallus.
10. The gametophytes bear male and female sex organs called antheridia and archegonia, respectively.

Sexual reproduction:
How do the sporophytes form?
Water is required for transfer of antherozoids to the mouth of archegonium. Fusion of male gamete with the egg present in the archegonium result in the formation of zygote. It undergoes divisions and forms multicellular well-differentiated sporophyte which is the dominant phase of the pteridophytes.

Distiquish between homosporous and heterosporous type or Heterospory is considered as important step in evolution why?
Majority members produce spores are of similar kinds such plants are called homosporous. Few members produce two kinds of spores, macro (large) and micro (small) spores, are-known as heterosporous. eg: Selaginella and Salvinia.

The megaspores and microspores germinate and give rise to female and male gametophytes, respectively. The development of the zygotes into young embryos take place within the female gametophytes. This event is a precursor to the seed habit considered an important step in evolution..
The pteridophytes are further classified into four classes:

1. Psilopsida(Psilotum)
2. Lycopsida (Selaginella, Lycopodium)
3. Sphenopsida (Equisetum
4. Pteropsida (Dryopteris, Pteris, Adiantum).

4. Gymnosperms:
Salient features:
1. They are naked seed bearing plants in which the ovules are not enclosed by ovary wall and remain exposed.

2. Tap roots have fungal association in the form of mycorrhiza (Pinus), while in some others (Cycas) small specialized roots called coralloid roots are associated with N2-fixing cyanobacteria.

3. The stems are unbranched (Cycas) or branched (Pinus, Cedrus).

4. The leaves are well-adapted to withstand extremes of temperature, humid ity and wind. .
How can conifers adapt to live in extreme temperature condition or water deficient soil?

• In conifers, the needle-like leaves that reduce the surface area. .
• Thick cuticle and
• sunken stomata

All these characters help to reduce water loss.

5. In Cycas the pinnate leaves persist for a few years.

6. They produce haploid microspores and megaspores i.e heterosporous. These spores are produced within sporangia that are borne omsporophylls which are arranged spirally along an axis to form compact strobili or cones. The strobili bearing microsporophylls and microsporangia are called male strobili.

The microspores develop into a male gametophytic generation. This reduced gametophyte is called a pollen grain. The pollen grain is released from the microsporangium. The cones bearing megasporophylls with ovules or megasporangia are called female strobili.

7. The male or female cones borne on the same tree (Pinus) or on different trees (Cycas).

Development of female qametophyte:
The ovules are borne on megasporophylls that contains nucellus. The megaspore mother cell of nucellus divides meiotically to form four megaspores. One of the megaspores enclosed within the megasporangium (nucellus) develops into a multicellular female gametophyte that bears two or more archegonia
1. The male and the female gametophytes remain within the sporangia retained on the sporophytes.

2. The pollen tube carrying the male gametes grows towards archegonia in the ovules and discharge their contents near the mouth of the archegonia. Following fertilisation, zygote develops into an embryo and the ovules into seeds. These seeds are not covered.

Which is the tallest tree species in world?
Giant redwood tree Sequoia is one of the tallest tree species.

5. Angiosperms (Flowering plants):
Salient features:
1. In this the seeds are enclosed by fruits.
Range of size:

• Microscopic-Wolfie
• Tall trees- Eucalyptus(o\ier 100 metres).

2. Two classes in angiosperms:

• Dicotyledons (two cotyledons in their seeds)
• Monocotyledons (one cotyledon)

3. The male sex organs in a flower is the stamen. Each stamen consists of a slender filament with an anther at the tip. The anthers produce pollen grains.

4. The female sex organs is the pistil or the carpel. Pistil consists of an ovary enclosing one to many ovules. The highly reduced female gametophytes (embryosacs) found within ovules.

5. Typical embryosac is 7 celled and 8 nucleate Each embryo-sac has a three-celled egg apparatus – one egg cell and two synergids, three antipodal cells and two polar nuclei. The polar nuclei eventually fuse to produce a diploid secondary nucleus. The cells of an embryo-sac is haploid.

Pollination and pollen tube:
Pollen grain from anther falls on the stigma of a pistil is termed as pollination. The pollen grains germinate and produce pollen tubes that reach the ovule. The pollen tubes enter the embryo-sac where two male gametes are discharged.

Double fertilization:
What are the products and process of double fertilization?
One of the male gametes fuses with the egg cell to form a zygote. This is called syngamy. The other male gamete fuses with the diploid secondary nucleus to produce the triploid primary endosperm nucleus (PEN). This is called Triple fusion. Because of the involvement of two fusions, this event is termed as double fertilization.

Post fertilization changes and significance of edosperm:
The zygote develops into an embryo and the PEN develops into endosperm which provides nourishment to the developing embryo. The synergids and antipodals degenerate after fertilisation. After fertilization ovules develop into seeds and the ovaries develop into fruits.

Plant Life Cycles And Alternation Of Generations:
In plants, both haploid and diploid cells can divide by mitosis. This ability leads to the formation of different plant bodies – haploid and diploid.

1. Haplontic life cycle:
How do gametophyte forms?
Meiosis in the zygote results in the formation of haploid spores. Then, these spores are divide mitotically and form the gametophyte.

What is the nature of sporophyte and gametophyte?
Sporophytic generation is represented only by the one-celled zygote. The dominant, photosynthetic phase is the free-living gametophyte.

2. Diplontic life cycle What is the nature of sporophyte and qametophyte?
The diploid sporophyte is the dominant, photosynthetic, independent phase of the plant. The gametophytic phase is represented by the single to few-celled haploid gametophyte. eg: gymnosperms and angiosperms.

3. Haplo-diplontic:
It is an intermediate condition in which both phases are multicellular and often free-living.

What is the nature of both sporophyte and gametophyte?
A dominant, independent, photosynthetic phase is represented by a haploid gametophyte and it alternates with the short lived multicelluler sporophyte dependent on the gametophyte. eg: Bryophytes and pteridophytes.

Algae in haplo-diplontic and diplontic stage:

• Ectocarpus, Polysiphonia and kelps are haplo-diplontic.
• Fucus, an alga is diplontic.

Students can Download Chapter 4 Biomolecules Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 4 Biomolecules

How To Analyse Chemical Composition?
Take any living tissue (a vegetable or a piece of liver, etc.) and grind it in trichloroacetic acid (Cl₃CCOOH) using a mortar and a pestle. The thick slurry is formed. Then it is passed through a cheese cloth or cotton getting two fractions.

1. Acid soluble fraction (Filtrate)
2. Acid-insoluble fraction.
   • All the carbon compounds from living tissues are called ‘biomolecules’.
   • The tissue is fully burnt, all the carbon compounds are oxidised to gaseous form (C02, water vapour) and are removed.
   • The remaining is called ‘ash’. It contains inorganic elements (like calcium, magnesium etc).
   • Inorganic compounds like sulphate, phosphate, etc., are also seen in the acid-soluble fraction.

Organic compounds under biological view are classified into

• Amino acids:
• Nucleotide bases
• Fatty acids etc.

Amino acids:

1. They are organic compounds containing four substituent groups occupying the four valency positions.
2. These are hydrogen, carboxyl group, amino group and a variable group designated as R group.

Based on the nature of R group there are many amino acids. However, those which occur in proteins are only of twenty one types.
The R group may be

• Hydrogen (the amino acid is called glycine)
• A methyl group (alanine)
• Hydroxyl methyl (serine), etc.

Based on number of amino and carboxyl groups, there are

A particular property of amino acids is due to ionizable nature of —NH₂ and —COOH groups

Fatty acid:
It has a carboxyl group attached to an R group.
The R group could be

1. A methyl (—CH₂)
2. Ethyl (—C₂H₅)

Carbon number varies in different fatty acids:

• Palmitic acid – 16 carbon atoms
• Arachidonic acid – 20 carbon atoms

Fatty acids are

• Lipids possess both glycerol and fatty acids.
• They are monoglycerides, or diglycerides or triglycerides.
• These are also called fats and oils based on melting point. Oils have lower melting point eg: gingely oil.
• Some lipids have phosphorous, they are called phospholipids. They are found in cell membrane. eg: lecithin

Nitrogen bases:

• They are (heterocyclic rings) adenine, guanine, cytosine, uracil, and thymine
• If they are found attached to a sugar, they are called nucleosides.
• If a phosphate group is found esterified to the sugar, they are called nucleotides.
• Nucleic acids like DNA and RNA consist of nucleotides only.

Diagrammatic representation of small molecular weight organic compounds in living tissues.

Primary And Secondary Metabolites:
Primary metabolites:
Organic compounds such as amino acids, sugars, etc.are belongs to primary metabolites. Primary metabolites play important role in normal physiologial processes.

Secondary metabolites:
When analyse plant, fungal and microbial cells the alkaloides, flavonoides, rubber, essential oils, antibiotics, coloured pigments, scents, gums, spices etc are found. These are called secondary metabolites. Many of them are useful to ‘human welfare’ (eg: rubber, drugs, spices, scents and pigments).

Biomacromolecules:
The acid insoluble fraction, has only four types of organic compounds i.e., proteins, nucleic acids, polysaccharides and lipids. These compounds, except lipids, have molecularweights in the range often thousand daltons and above.

Lipids, whose molecularweights do not exceed 800 Da, come under acid insoluble fraction. Hence Lipids are not macromolecules.

Biomicromolecules and biomacromolecules:
Molecular weights less than one thousand dalton are referred to as micromolecules or simply biomolecules while those which are found in the acid insoluble fraction are called macromolecules or biomacromolecules.

Proteins:
Proteins (heteropolymer)are linear chains of amino acids linked by peptide bonds i.e polymer of amino acids There are 21 types of amino acids (eg: alanine, cysteine, proline, tryptophan, lysine, etc.)
Some Proteins and their Function:

• Dietary proteins are the source of essential amino acids.
• Therefore, amino acids are essential or non-essential.
• Essential amino acids obtained through food.

Proteins carry out many functions in living organisms:

1. some transport nutrients across cell membrane
2. some fight infectious organisms
3. Collagen is the most abundant protein in animal world and
4. Ribulose bisphosphate Carboxylase – Oxygenase (RUBISCO) is the most abundant protein in the biosphere.

POLYSACCHARIDES
1. Polysaccharides are long chains of sugars.

2. Forexamplecellulose(homopolymer)is a polysaccharide consist of only one type of monosaccharide i.e. glucose.

3. Starch is store house of energy in plant tissues but animals have glycogen as energy source.

4. Inulin is a polymer of fructose.

5. In a polysaccharide eg glycogen, the right end is called the reducing end and the left end is called the non reducing end.

Starch forms helical secondary structures:

1. Starch can hold l₂ molecules in the helical portion. This reaction product blue in colour.
2. Cellulose does not contain complex helices and hence cannot hold l₂.
3. Cotton fibre is cellulose
4. The complex polysaccharides have as building blocks such as amino-sugars (eg: glucosamine, N— acetyl galactosamine, etc.).
5. Exoskeletons of arthropods have a complex polysaccharide called chitin (heteropolymers)

Nucleic Acids:
Nucleic acids are the another macromolecule that found in the acid insoluble fraction of living tissues. For nucleic acids, the building block is a nucleotide.

Components of nucleic acid:

1. Heterocyclic compound(adenine, guanine, uracil, cytosine and thymine).
2. Monosaccharide and
3. A phosphoric acid or phosphate.

The sugar found in polynucleotides is either ribose (a monosaccharide pentose) or 2’ deoxyribose.

Nature of pentose sugar in DNA and RNA:
A nucleic acid containing deoxyribose is called deoxyribonucleic acid (DNA) while that which contains ribose is called ribonucleic acid (RNA).

Structure Of Proteins (Proteins are heteropolymers containing many amino acids):
Primary structure:
The sequence of amino acid in which the left end represented by the first amino acid (N— terminal amino acid )the right end represented by the last amino acid (C— terminal amino acid). This sequence forms linear structure. It is called the primary structure.

Primary structure of a portion of a hypothetical protein. N and C refer to the two termini of every protein. Single letter codes and three letter abbreviations for amino acids are also indicated.

Secondary structure:
The primary structure have rigid rod like appearance which is folded in the form of a helix (similar to a revolving staircase). It appears as right handed helices. It is called the secondary structure. Secondary structures exhibited by DNA is the Watson-Crick model. In this DNA exists as a double helix.

Tertiary structure:
The long protein chain is also folded upon itself like a hollow wollen ball, it called the tertiary structure. This gives us a 3-dimensional view of a protein. Tertiary structure is necessary for the many biological activities of proteins.

Quaternary structure:
Some proteins are assembled by more than one polypeptide chains .This is called the quaternary structure Adult human haemoglobin consists of 4 subunits. Two of these are identical to each other. Hence, two subunits are of a type and two subunits are of p type together constitute the human haemoglobin (Hb).

Nature Of bond linking Monomers In A Polymer:
1. Peptide bond:
In a protein, amino acids are linked by a peptide bond which is formed when the carboxyl (—COOH) group of one amino acid reacts with the amino (-NH₂) group of the next amino acid with the elimination of a water.

2. Glvcosidic bond:
In a polysaccharide the individual monosaccharides are linked by a glycosidic bond. This bond is also formed by dehydration.

3. Phosphodiester Bond:
In a nucleic acid a phosphate moiety links the 3′-carbon of one sugar of one nucleotide to the 5′-carbon of the sugar of the succeeding nucleotide. The bond between the phosphate and hydroxyl group of sugar is called phosphodiester bond

DNA Structure:

1. The two strands of polynucleotides are antiparallel i.e., run in the opposite direction.
2. The backbone is formed by the sugar-phosphate-sugar chain.
3. The nitrogen bases are A and G of one strand base pairs with T and C, respectively
4. There are two hydrogen bonds between A and T but three hydrogen bonds are present between G and C.
5. Each strand appears like a helical staircase.
6. At each step of ascent, the strand turns 36°.
7. One full turn of the helical strand have ten steps or ten base pairs.
8. The pitch is 34A°. The distance between each base pairs is 3.4A°.
9. This form of DNA is called B-DNA.

Dynamic State Of Body Constituents – Concept Of Metabolism:
Biomolecules are constantly being changed into some other biomolecules and also made from some other biomolecules. This is called turn over. This breaking and making is through chemical reactions constantly occurring in living organisms called as metabolism.

Metabolic reactions and transformation of biomolecules:

1. removal of CO₂ from amino acids making an amino acid into an amine,
2. removal of amino group in a nucleotide base and
3. hydrolysis of a glycosidic bond in a disaccharide
   • Majority of these metabolic reactions are always linked to some other reactions. This series of linked reactions called metabolic pathways.
   • These metabolic pathways are similar to the automobile traffic in a city.
   • Another feature of these metabolic reactions is that every chemical reaction is a catalysed reaction.
   • The catalysts which hasten the rate of a given metabolic conversation are also proteins. These proteins with catalytic power are named enzymes.

Metabolic Basis For Living:

1. Metabolic pathways involves two processes The synthesis step is called anabolic pathways. The degradation step is called catabolic pathways.
2. Catabolic pathways lead to the release of energy.
3. For example, when glucose is degraded to lactic acid in our skeletal muscle, energy is liberated which stored in the form of chemical bonds, when needed, this bond energy is utilized.

Which is the energy currency of a cell?

• The energy currency in living systems is the bond energy in a chemical called adenosine triphosphate (ATP).

The Living State:

• All living organisms exist in a steady-state characterised by concentrations of each of these biomolecules.
• These biomolecules are in a metabolic flux. Any chemical or physical process moves spontaneously to equilibrium.
• The steady state is a non-equilibirium state. The systems at equilibrium cannot perform work. As living organisms work continuously, they cannot afford to reach equilibrium.

Metabolism provides a mechanism for the production of energy. Hence the living state and metabolism are synonymous. Without metabolism there cannot be a living state.

Enzymes:

Enzvme activity:

• The tertiary structure is biologically active, an active site of an enzyme is a crevice or pocket into which the substrate fits.
• Thus enzymes, through their active site, catalyse reactions at a high rate.
• Enzymes are damaged at high temperatures (say above 40°C).
• Some enzymes isolated from organisms who normally live under extremely high temperatures (eg: hot vents and sulphur springs), are stable and retain their catalytic power even at high temperatures (upto 80° – 90°C).
• Thermal stability is thus an important quality of such enzymes isolated from thermophilic organisms.

Chemical Reactions:
Chemical compounds undergo two types of changes.
1. Physical change:
It involves the change in shape without breaking of bonds. eg: when ice melts into water, or when water becomes a vapour.

2. Chemical reaction/change:
When bonds are broken and new bonds are formed during transformation, this will be called a chemical reaction.Eg. Hydrolysis of starch into glucose is an organic chemical reaction. Rate of a physical or chemical process refers to the amount of product formed per unit time.

Role of enzvme in the rate of chemical reaction:
In the absence of any enzyme this reaction is very slow, with about 200 molecules of H₂CO₃ being formed in an hour. But using an carbonic anhydrase, the reaction speeds dramatically with about 600,000 molecules being formed every second.

The enzyme has accelerated the reaction rate by about 10 million times. A multistep chemical reaction, when each of the steps is catalysed by the same enzyme complex or different enzymes, is called a metabolic pathway.

1. In glycolysis glucose becomes pyruvic acid through ten different enzyme catalysed metabolic reactions.
2. Under normal aerobic conditions, pyruvic acid is formed.
3. In yeast, during fermentation, the same pathway leads to the production of ethanol (alcohol).
4. In our skeletal muscle, under anaerobic conditions, lactic acid is formed.

How do Enzymes bring about High Rates of Chemical Conversions?
The chemical which is converted into a product is called a ‘substrate’. Hence enzymes, i.e. proteins with three dimensional structures including an ‘active site’ convert a substrate (S) into a product (P).

What is the transition state?
During the state where substrate is bound to the enzyme active site, a new structure of the substrate called unstable transition state is formed. Then the bond breaking/making is completed, the product is released from the active site. The y-axis represents the potential energy content.

The x-axis represents the progression of the structural transformation or states through the ‘transition state’. If ‘P’ is at a lower level than ‘S’, the reaction is an exothermic reaction one need not to supply energy (by heating) in order to form the product.

However, whether it is an exothermic or spontaneous reaction or an endothermic or energy requiring reaction, the ‘S’ has to go through a much higher energy state or transition state. The difference in average energy content of ‘S’ from that of this transition state is called ‘activation energy’.

Enzymes bring down energy barrier making the transition of ‘S’ to ‘P’ more easy. Catalysed reactions proceed at rates faster than that of uncatalysed ones.

Nature of Enzyme Action:

Each enzyme (E) has a substrate (S) binding site in its molecule so that a highly reactive enzyme-substrate complex (ES) is produced. This complex is short-lived and dissociates into its products.

The catalytic cycle of an enzyme action can be described in the following steps:

Factors Affecting Enzyme Activity:

The activity of an enzyme can be affected by temperature, pH, change in substrate concentration.
1. Temperature and pH:
Each enzyme shows its highest activity at a particular temperature and pH called the optimum temperature and optimum pH. Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.

2. Concentration of Substrate:
With the increase in substrate concentration, the velocity of the enzymatic reaction rises at first. The reaction ultimately reaches a maximum velocity (V_max) which is not increased by further rise in concentration of the substrate because the enzyme molecules are saturated there are no free enzyme molecules to bind with the additional substrate molecules

Enzyme inhibition:
When the binding of the chemical shuts off enzyme activity, the process is called inhibition and the chemical is called an inhibitor. When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as competitive inhibitor. eg: Inhibition of succinic dehydrogenase by malonate which closely resembles the substrate succinate in structure. Such competitive inhibitors are often used in the control of bacterial pathogens.

Classification and Nomenclature of Enzymes:
Enzymes are divided into 6 classes.
1. Oxidoreductases/dehvdroaenases:
Enzymes which catalyse oxidoreduction between two substrates S and S’ eg:

2. Transferases:
Enzymes catalysing a transfer of a group, G (other than hydrogen) between a pair of substrate S and S’ eg:
\(\mathbf{S}-\mathbf{G}+\mathbf{S}^{‘} \longrightarrow \mathbf{S}+\mathbf{S}^{‘}-\mathbf{G}\)

3. Hydrolases:
Enzymes catalysing hydrolysis of ester, ether, peptide, glycosidic, C – C, C – halide or P – N bonds.

4. Lyases:
Enzymes that catalyse removal of groups from substrates by mechanisms other than hydrolysis leaving double bonds.

5. Isomerases:
Includes all enzymes catalysing inter-conversion of optical, geometric or positional isomers.

6. Lyases:
Enzymes catalysing the linking together of 2 compounds, eg: enzymes which catalyse joining of C – O, C – S, C – N, P – O etc. bonds.

Co-factors:
Enzymes are composed of one or several polypeptide chains and non-protein constituents called cofactors. They are bound to the enzyme to make the enzyme catalytically active. The protein part of the enzymes is called the apoenzyme.
Three kinds of cofactors are

1. prosthetic groups
2. co-enzymes
3. Metal ions.

1. Prosthetic groups:
They are organic compounds that are tightly bound to the apoenzyme. For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen. Haem is the prosthetic group and it is a part of the active site of the enzyme.

2. Co-enzymes:
They are also organic compounds loosely bound to apoenzyme for catalysis. Co-enzymes serve as co-factors in a number of different enzyme-catalyzed reactions. Many coenzymes are vitamins eg: coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.

2. Metations:
Zinc is a cofactor for the proteolytic enzyme carboxypeptidase. Catalytic activity is lost when the co-factor is removed from the enzyme.

Students can Download Chapter 11 Chemical Coordination and Integration Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 11 Chemical Coordination and Integration

What is neural system?
The neural system and the endocrine system coordinate and regulate the physiological functions in the body.

Endocrine Glands And Hormones:
Endocrine glands lack ducts and are called ductless glands. Their secretions are called hormones.

Human Endocrine System
The endocrine glands are located in different parts of our body constitute the endocrine system. Pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus and gonads (testis in males and ovary in females) are the organised endocrine bodies in our body.

In addition to these, some other organs, eg: gastrointestinal tract, liver, kidney, heart also produce hormones.

The Hypothalamus:
The hypothalamus is the basal part of diencephalon, forebrain and it regulates body functions. The hormones produced by hypothalamus are of two types

1. The releasing hormones (which stimulate secretion of pituitary hormones)
2. The inhibiting hormones (which inhibit secretions of pituitary hormones).

For example,

These hormones originating in the hypothlamic neurons, pass through axons and are released from their nerve endings reach the pituitary gland through a portal circulatory system and regulate the functions of the anterior pituitary. The posterior pituitary is under the direct neural regulation of the hypothalamus.

The Pituitary Gland:
The pituitary gland is located in a bony cavity called sella tursica. It is divided into an adenohypophysis and a neurohypophysis.

Adenohypophysis:
It consists of two portions, pars distalis and pars intermedia. The pars distalis region of pituitary, commonly called anterior pituitary, produces growth hormone (GH), prolactin (PRL), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH) and follicle stimulating hormone (FSH).

Pars intermedia secretes only one hormone called melanocyte stimulating hormone (MSH). Pars intermedia is almost merged with pars distalis.

Neurohvpophysis:
It is also known as posterior pituitary, stores and releases two hormones called

1. Oxytocin
2. vasopressin

Function:
These are synthesised by the hypothalamus and are transported to neurohypophysis.

Growth hormone:
Over-secretion of GH stimulates abnormal growth of the body leading to gigantism and low secretion of GH results in stunted growth resulting in pituitary dwarfism. Prolactin regulates the growth of the mammary glands and formation of milk in them.

TSH stimulates the synthesis arid secretion of thyroid hormones from the thyroid gland. ACTH stimulates the synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex. LH and FSH stimulate gonadal activity and called as gonadotrophins.

Activity of LH and FSH in males and females:
In males, LH stimulates the synthesis and secretion of hormones called androgens from testis. In males, FSH and androgens regulate spermatogenesis. In females, LH induces ovulation of fully mature follicles (graafian follicles) and maintains the corpus luteum, formed from the graafian follicles after ovulation.

In females FSH stimulates growth and development of the ovarian follicles. MSH acts on the melanocytes (melanin containing cells) and regulates pigmentation of the skin. Oxytocin stimulates a vigorous contraction of uterus at the time of child birth, and milk ejection from the mammary gland.

Hormone in water reabsorption:
Vasopressin acts on kidney and stimulates resorption of water and electrolytes by the distal tubules and thereby reduces loss of water through urine (diuresis). Hence, it is also called as anti-diuretic hormone (ADH).

The Pineal Gland:
The pineal gland is located on the dorsal side of forebrain. It secretes a hormone called melatonin. It regulates 24-hour (diurnal) rhythm of our body. For example, it helps in maintaining sleep-wake cycle, body temperature, metabolism, pigmentation, the menstrual cycle as well as our defense capability.

Thyroid Gland:
It is composed of two lobes which are located on either side of the trachea. The thyroid gland is composed of follicles and stromal tissues. The follicular cells synthesise two hormones, tetraiodothyronine or thyroxine (T4) and triiodothyronine (T3). Deficiency of iodine in our diet results in hypothyroidism and enlargement of the thyroid gland called goitre.

Hypothyroidism during pregnancy causes defective development and maturation of the growing baby leading to stunted growth (cretinism), mental retardation, low intelligence quotient, abnormal skin, deaf-mutism, etc.

In adult women, hypothyroidism cause the occurrence of irregular menstrual cycle. Due to cancer of the thyroid gland the synthesis and secretion of the thyroid hormones is increased to abnormal high levels leading to a condition called hyperthyroidism.

Parathyroid Gland:
It is present on the back side of the thyroid gland and secrete a peptide hormone called parathyroid hormone (PTH).

PTH also stimulates reabsorption of Ca²⁺ by the renal tubules and increases Ca²⁺ absorption from the digested food. Hence PTH is a hypercalcemic hormone i.e., it increases the blood Ca²⁺ levels. Along with TCT, it plays a significant role in calcium balance in the body.

Thymus:
The thymus gland is located on the dorsal side of the heart and the aorta and plays a major role in the development of the immune system.

Adrenal Gland:
It is located at the anterior part of each kidney. The gland is composed of inner adrenal medulla, and outside the adrenal cortex.

Adrenal medulla:

Adrenaline and noradrenaline are secreted during emergency situations and are called emergency hormones or hormones of Fight or Flight. These hormones increase alertness, pupilary dilation, piloerection (raising of hairs), sweating, etc.

These hormones increase the heart beat, the strength of heart contraction and the rate of respiration. Catecholamines stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood. They also stimulate the breakdown of lipids and proteins.

Adrenal cortex:
It is divided into three layers, called

1. zona reticularis (inner layer)
2. zonafasciculata (middle layer)
3. zona glomerulosa (outer layer).

The secretory hormones are commonly called as corticoids. They are involved in carbohydrate metabolism called as glucocorticoids. eg: Cortisol.

Function:
It maintains the cardio-vascular system as well as the kidney functions, suppresses the immune response and stimulates the RBC production. Corticoids, which regulate the balance of water and electrolytes in our body are called mineralocorticoids. eg: Aldosterone.

Glucocorticoids stimulate, gluconeogenesis, lipolysis and proteolysis and inhibit cellular uptake and utilisation of amino acids. Aldosterone stimulates the reabsorption of Na⁺ and water and excretion of K⁺ and phosphate ions.

Hence it helps in the maintenance of electrolytes, body fluid volume, osmotic pressure and blood pressure. Androgenic steroids secreted by the adrenal cortex which play a role in the growth of axial hair, pubic hair and facial hair during puberty.

Pancreas:
It acts as both exocrine and endocrine gland. The endocrine consists of ‘Islets of Langerhans’.

Glucagon is a peptide hormone maintains the normal blood glucose levels, stimulates glycogenolysis – increased blood sugar (hyperglycemia),stimulates the process of gluconeogenesis – contributes to hyperglycemia. Insulin is a peptide hormone, which enhances cellular glucose uptake and utilisation.

As a result, there is a rapid movement of glucose from blood to hepatocytes and adipocytes resulting in decreased blood glucose levels (hypoglycemia). Insulin also stimulates conversion of glucose to glycogen (glycogenesis) in the target cells.

Prolonged hyperglycemia leads to a complex disorder called diabetes mellitus which is associated with loss of glucose through urine and formation of harmful compounds known as ketone bodies.

Testis:
A pair of testis is present in the scrotal sac of male individuals Testis performs dual functions as a primary sex organ as well as an endocrine gland. Testis is composed of seminiferous tubules and stromal or interstitial tissue. The Leydig cells or interstitial cells, which produce a group of hormones called androgens mainly testosterone.

Androgens regulate the development, maturation and functions of the male accessory sex organs like epididymis, vas deferens, seminal vesicles, prostate gland, urethra etc.

Androgens also stimulate muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice, spermatogenesis (formation of spermatozoa), influence the male sexual behaviour (libido).

These hormones produce anabolic (synthetic) effects on protein and carbohydrate metabolism.

Ovary:
It is the primary female sex organ which produces one ovum during each menstrual cycle. Ovary produces two groups of steroid hormones called estrogen and progesterone. The estrogen is are secreted by the growing ovarian follicles. After ovulation, the ruptured follicle is converted to a structure called corpus luteum, which secretes progesterone.

Estrogens involved in stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g., high pitch of voice, etc.), mammary gland development, regulate female sexual behaviour.

Progesterone supports pregnancy, stimulates the formation of alveoli (sac-like structures which store milk) and milk secretion.

Hormones Of Heart Kidney And Gastrointestinal Tract:
The atrial wall of our heart secretes a very important peptide hormone called atrial natriuretic factor (ANF), which decreases blood pressure. When blood pressure is increased, ANF is secreted which causes dilation of the blood vessels. This reduces the blood pressure.

The juxtaglomerular cells of kidney produce a peptide hormone called erythropoietin which stimulates erythropoiesis (formation of RBC). The gastro-intestinal tract secrete four major peptide hormones, namely gastrin, secretin, cholecystokinin (CCK) and gastric inhibitory peptide (GIP).

Gastrin stimulates the secretion of hydrochloric acid and pepsinogen. Secretin stimulates secretion of water and bicarbonate ions. CCK acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice, respectively. GIP inhibits gastric secretion and motility.

Mechanism Of Hormone Action:
Hormones bind to specific proteins called hormone receptors Hormone receptors present on the cell membrane of the target cells are called membrane-bound receptors and the receptors present inside the target cell are called intracellular receptors.

Binding of a hormone to its receptor leads to the formation of a hormone-receptor complex. Hormone- Receptor complex formation leads to certain biochemical changes in the target tissue. On the basis of their chemical nature, hormones can be divided into groups.

1. peptide,
2. polypeptide,
3. protein hormones (eg: insulin, glucagon, pituitary hormones, hypothalamic hormones, etc.)
   • steroids (eg: cortisol, testosterone, estradiol and progesterone)
   • iodothyronines (thyroid hormones)
   • amino-acid derivatives (eg: epinephrine).

Hormones which interact with membrane-bound receptors do not enter the target cell, but generate second messengers (eg: cyclic AMP, IP3, Ca^++, etc) which in turn regulate cellular metabolism. Hormones which interact with intracellular receptors (eg: steroid hormones, iodothyronines, etc.) regulate gene expression or chromosome function.

Exophthalmic goitre, also called Grave’s disease:
This occurs due to hyperthyroidism i.e the excessive secretion of thyroxine hormone is accompanied by the enlargement of the thyroid glands. It is an autoimmune disease where patients produce antibodies that act on the thyroid glands to increase thyroxine hormone production and thyroid size. eg: Patients suffering from cancerof thyroid glands.

The symptoms are elevated metabolic rate, sweating, rapid and irregular heartbeat, weight loss despite increased appetite, frequent bowel movement and nervousness. Some patients may also experience exophthalmos (or protrusion of the eyeballs). Thus this condition is also known as exophthalmic goitre.

Addison’s’ disease:
The hyposecretory disorder of the adrenal cortex or destruction of adrenal cortex in diseases such as tuberculosis leads to deficit of both glucocorticoids and mineralocorticoids. This condition is known as Addison’s disease. The symptoms are loose weight, their blood glucose and sodium levels drop and potassium levels rise.

NCERT SUPPLEMENTARY SYLLABUS
Exophthalmic goitre, also called Grave’s disease:
This occurs due to hyperthyroidism i.e the excessive secretion of thyroxine hormone is accompanied by the enlargement of the thyroid glands.

It is an autoimmune disease where patients produce antibodies that act on the thyroid glands to increase thyroxine hormone production and thyroid size. eg: Patients suffering from cancer of thyroid glands.

The symptoms are elevated metabolic rate, sweating, rapid and irregular heartbeat, weight loss despite increased appetite, frequent bowel movement and nervousness. Some patients may also experience exophthalmos (or protrusion of the eye balls). This condition is also known as exophthalmic goitre.

Addison’s’ disease:
The hyposecretory disorder of the adrenal cortex or destruction of adrenal cortex in diseases such as tuberculosis leads to deficit of both glucocorticoids and mineralocorticoids.

This condition is known as Addison’s disease. The symptoms are weight loss, blood glucose and sodium levels drop and potassium levels rise.

Students can Download Chapter 12 Accounting System Using Database Management System Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 12 Accounting System Using Database Management System

Summary:
Accounting Reports:
A report displays information that is acquired from data processing and transformation in an organised manner. Reports tend to reduce the level of uncertainty associated with decision-makers and also influence their positive actions.

The output of the computerised accounting system are accounting reports. Financial accounting reports such as Cash book, Bank book, Ledger and Trial Balance may be generated in Access by adhering to report generation process.

Using Access for Producing Reports:
In Access, the reports are created by designing a report, identifying its information requirement, creating the queries in SQL to generate such information so that the final SQL statement provides the record set of information to the report design. Different Models of database design require different sets of SQL statements to produce different types of reports.

Queries Access:
There are several types of queries in Access that may be used to generate information. Such queries are called select queries because they are used to select records from the given set of records. There are three ways in which these queries may be created in Access: Wizard. Design View and SQL view method.

Designing Reports in Access:
A report in Access may be designed in three ways: Auto Report. Wizard and Design View method. An SQL statement (or query) is capable of displaying records containing fields from across a number of data tables.

A typical report in Access has the structure that consists of Report header, Page header, Group header, Details, Group footer, Page footer and Report footer.

Students can Download Chapter 11 Structuring Database for Accounting Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 11 Structuring Database for Accounting

Summary:
Database Concepts:

1. Reality: It consists of different components of an organisation such as people, facilities and other resources.

2. Data: It represents data concerning people, places, objects entities, events, etc., and non-financial 14 nature.

3. Database: It was a shared collection of inter-related data tables, tiles or structures which are designed to most varied information needs of all organisations.

4. International: Processed data organisation in a form that is suitable for decision-making.

5. DBMS: A collection of programmes that enable users to create and maintain a database.

Database System Concepts and Architecture Data model:
Collection of concepts used to describe the structure of a database.

1. Database Schemes: The description of a database is called its scheme.
2. Database State and Instances: Data in a database at a particular movement is called database state.

Entity-Relationship (ER) Model:
An important concept of data model mostly used in a database-oriented application. The major elements of ER model are entities attributes, identities and relationship that are used to express reality for which a database is to be designed.

Relation Data Model (RDM):
It represents the database at collection of tables comprising different volumes. It consists of rows and columns. The table name and column name are used to help in interpreting the meaning of volumes of each row. Each row of table is called a data record.

Students can Download Chapter 10 Applications of Computers in Accounting Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 10 Applications of Computers in Accounting

Summary:
Meaning of a Computer:
The computer is an electronic device capable of performing a variety of operations as desired by a set of instructions.

Elements of a Computer System:

1. Hardware
2. People
3. Data Connectivity
4. Software
5. Procedure

Capabilities of a Computer:

1. Speed
2. Reliability
3. Storage
4. Accuracy
5. Versatility

Need for Computers in Accounting:
The advent of globalisation has resulted in a rise in business operations. Consequently, every medium and large-sized organisations require well-established information system in order to generate information required for decision making and achieving the organisational objectives. This made Information technology to play a vital role in supporting business operations.

MIS and Accounting Information System:
A management information system provides information necessary to take decisions and manage an organisation effectively. Accounting information system on the other hand identifies, collects, processes and communicates economic information about an entity to a wide variety of users.

Accounting Reports:
Information supplied to meet a particular need is called a report. An accounting report must fulfil the following conditions:

• Relevance
• Timeliness
• Accuracy
• Completeness
• Summarisation

Computerised Accounting System:
A computerised accounting system is an accounting information system that processes the financial transactions and events to produce reports as per user requirements. It is based on the concept of database and has two basic requirements:

1. Accounting framework and
2. Operating Procedure.

Advantages of Computerised Accounting System:

1. Speed
2. Reliability
3. Scalability
4. Efficiency
5. MIS Reports
6. Storage and Retrieval
7. Accuracy
8. Up-to-date
9. Legibility
10. Quality Report
11. Real-time user interface
12. Motivation and Employees interest
13. Automated document production

Limitations of Computerised Accounting System:

• Cost of training
• Disruption
• Breach of security
• Inability to check unanticipated errors
• Staff Opposition
• System failure
• III-effects on health

Categories of Accounting Packages:

• Ready-to-Use
• Tailored
• Customised

Students can Download Chapter 9 Accounts from Incomplete Records Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 9 Accounts from Incomplete Records

Summary:
Incomplete Records:
Incomplete records refer to a lack of accounting records according to the double-entry system. It is an incomplete, unscientific and unsystematic method of keeping the books of accounts of a trader.

Computation of profit and loss from incomplete records:
The statement of affairs is used to compute capital when a firm has a set of incomplete records. It shows assets on one side and the liabilities on the other as in the case of a balance sheet. The difference between the totals of the two sides is the capital.

Format of Statement of Affairs:
Statement of Affairs as on …………………

The statement of profit or loss is prepared to ascertain the exact amount of profit or loss made during the year.

Format of Statement of Affairs:
Statement of Profit or Loss for the year ended ………….

Preparation of Profit and Loss Account and Balance Sheet. (Conversion method):
In order to prepare final accounts from incomplete records, we have to find out the missing figures by making further computations and adjustments to the available information. The following are the steps to prepare the final accounts from incomplete records.

(i) Preparation of statement of Affairs.
(ii) Preparation of cash book
(iii) Ascertaining credit purchases and credit sales:-
Credit purchase can be ascertained by preparing a statement or by preparing Total creditors Account.

Format of Total Creditors Account:

Format of Total Creditors Account:

(a) Bills Receivable and Bills payable Accounts are prepared for finding out their opening or closing balances or for finding out the amount of bills accepted or bills received during the year.

(b) The proforma of total bills receivable account and total bills payable account. The proforma of total bills receivable account and total bills payable account is shown.

Total Bills Receivable Account:

Total Bills Payable Account:

(iv) Calculate:

• Total purchase by adding cash purchases and credit purchases.
• Total sales by adding cash sales and credit sales.

(v) Prepare Trial balance with the given information and missing information ascertained:
The components of the trial balance and their sources of information are summarised below

(vi) Prepare final accounts in the usual manner.

Students can Download Chapter 8 Financial Statements – I & II Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 8 Financial Statements – I & II

Summary:
Financial Statements:
Meaning and types Financial statements are the statements which present periodic reports on the process of business enterprises and the results achieved during a given period. Financial statement includes trading, profit & loss account, balance sheet and other statements.

Trading and Profit & Loss Account:
Trading and Profit & Loss account is prepared to ascertain the net result of business operations during a given period.

Format of Trading and Profit & Loss Account (In horizontal form):
Trading and Profit & Loss Account for the year ended ………………

Need for Adjustment:
For the preparation of financial statements, it is necessary that all adjustments arising out of the accural basis of accounting are made at the end of the accounting period. Entries which are given outside the trial balance are called adjustment entries.

Treatment of various types of adjustments:

Balance Sheet:
The balance sheet is a statement of assets and liabilities of a business enterprises and shows the financial position at a given date. It is not an account. It is only a statement.
Assets and liabilities shown in the balance sheet are marshalled in order to liquidity or in order to permanence.

Format of Balance Sheet (In horizontal form)
Balance sheet as on …………….

The Performa of income statement and balance sheet in vertical form.

Income Statement for the period ended ……..

Balance sheet as on………..

Students can Download Chapter 10 Neural Control and Coordination Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 10 Neural Control and Coordination

What is coordination?
Coordination is the process through which two or more organs interact and complement the functions of one another.

Neural System
The neural system of all animals is composed neurons that receive and transmit different kinds of stimuli.

Neural system in lower forms

• The neural organisation is very simple in lower invertebrates.
• For example, in Hydra it is composed of a network of neurons.
• The neural system is better organised in insects, where a brain is present.

The vertebrates have a more developed neural system.

Human Neural System
The human neural system is divided into two parts:

• The CNS includes the brain and the spinal cord and is the site of information processing and control.
• The PNS comprises of all the nerves of the body associated with the CNS.

The nerve fibres of the PNS are of two types:

Function of afferent efferent of nerve fibres:
The afferent nerve fibres transmit impulses from tissues/organs to the CNS. The efferent fibres transmit regulatory impulses from the CNS to the peripheral tissues/organs.
The PNS is divided into two divisions

1. Somatic neural system
2. Autonomic neural system.

Function:
The somatic neural system relays impulses from the CNS to skeletal muscles. The autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body.
The autonomic neural system is classified into

1. sympathetic neural system
2. parasympathetic neural system.

Neuron As Structural And Functional Unit Of Neural System
A neuron is composed of three major parts,

1. The cell body contains cytoplasm with cell organelles and certain granular bodies called Nissl’s granules.

2. Repeated branches project out of the cell body are called dendrites.

3. The axon is a long fibre, the distal end of which is branched. Each branch terminates as a bulb-like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters. Based on the number of axon and dendrites, the neurons are divided into three types,

• multipolar (with one axon and two or more dendrites; found in the cerebral cortex)
• bipolar (with one axon and one dendrite, found in the retina of eye)
• unipolar (cell body with one axon only found usually in the embryonic stage).

4. The myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon.

5. The gaps between two adjacent myelin sheaths are called nodes of Ranvier.

6. Myelinated nerve fibres are found in spinal and cranial nerves.

8. Non-myelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath around the axon, and is commonly found in autonomous and the somatic neural systems.

Generation and Conduction of Nerve Impulse
Neurons are excitable cells because their membranes are in a polarized state.
In resting state of neuron:
The axonal membrane is more permeable to potassium ions (K⁺) and impermeable to sodium ions (Na⁺) and negatively charged proteins present in the axoplasm. The fluid outside the axon contains a low concentration of K⁺, a high concentration of Na⁺ and thus form a concentration gradient.

These ionic gradients are maintained by the active transport of ions by the sodium-potassium pump which transports 3 Na⁺ outwards for 2 K⁺ into the cell.

As a result, the outer surface of the axonal membrane possesses a positive charge while its inner surface becomes negatively charged and therefore is polarised. The electrical potential difference across the resting plasma membrane is called as the resting potential.

When a stimulus is applied at a site on the polarised membrane:
The membrane freely permeable to Na and influx of Na⁺ followed by the reversal of the polarity at that site, i.e., the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged.

This is called depolarized state. The electrical potential difference across the plasma membrane is called the action potential At sites immediately ahead, the axon membrane has a positive charge on the outer surface and a negative charge on its inner surface. As a result, a current flows on the inner surface from site A to site B.

On the outer surface current flows from site B to site A to complete the circuit of current flow. Hence, the polarity at the site is reversed, and an action potential is generated at site B. Thus, the impulse (action potential) generated at site A arrives at site B. The sequence is repeated along the length of the axon and consequently the impulse is conducted.

Transmission of Impulses
A nerve impulse is transmitted from one neuron to another through junctions called synapses. The junction between pre-synaptic neuron and a post-synaptic neuron is called synaptic cleft. There are two types of synapses, namely

At electrical synapses, erlectrical current flowdirectly from one neuron into the other across these synapses. It is very similar to impulse conduction along a single axon, impulse transmission across an electrical synapse is always faster than that across a chemical synapse.

At a chemical synapse, the membranes ofthepre-and post-synaptic neurons are separated by a fluid-filled space called synaptic cleft Chemicals called neurotransmitters are involved in the transmission of impulses at these synapses.

The released neurotransmitters bind to the specific receptors, present on the post-synaptic membrane. This binding opens ion channels allowing the entry of ions which can generate a new potential in the post- synaptic neuron.

Central Neural System
It controls the voluntary movements such as balance of the body, functioning of vital involuntary organs (e.g., lungs, heart, kidneys, etc.), thermoregulation, hunger and thirst, circadian (24-hour) rhythms of our body, activities of several endocrine glands and human behaviour.

It is also the site for processing of vision, hearing, speech, memory, intelligence, emotions and thoughts. The human brain is well protected by the skull. Inside the skull, the brain is covered by cranial meninges consisting of an outer layer called dura mater, a very thin middle layer called arachnoid and an inner layer called pia mater.

The brain is divided into three major parts:

• forebrain
• midbrain
• hindbrain

Forebrain
The forebrain consists of cerebrum, thalamus and hypothalamus. Cerebrum forms the major part of the human brain. Cerebrum divided longitudinally into two halves the left and right cerebral hemispheres. The hemispheres are connected by nerve fibres called corpus callosum.

The layer of cells which covers the cerebral hemisphere is called cerebral cortex. The cerebral cortex is referred to as the grey matter .The cerebral cortex contains motor areas, sensory areas and large regions These regions called as the association areas.They are responsible functions like memory and communication.

The inner part of cerebral hemisphere gives white appearance to the layer and called as the white matter. Hypothalamus lies at the base of the thalamus contains a number of centres which control body temperature, urge for eating and drinking. Hypothalamus secrete hormones called hypothalamic hormones.

he inner parts of cerebral hemispheres and a group of associated deep structures like amygdala, hippocampus, etc., form a complex structure called the limbic lobe or limbic system. Along with the hypothalamus,

Midbrain
The midbrain is located between the thalamus/hypothalamus of the forebrain and pons of the hindbrain. A canal called the cerebral aqueduct passess through the midbrain.

The dorsal portion of the midbrain consists mainly of four round swellings (lobes) called corpora quadrigemina. Midbrain and hindbrain form the brain stem..

Hindbrain
The hindbrain comprises pons, cerebellum and medulla (also called the medulla oblongata). Pons consists of fibre tracts that interconnect different regions of the brain. Cerebellum provide the additional space for many more neurons.

The medulla of the brain is connected to the spinal cord. The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions.

Reflex Action And Reflex Arc
It involves the sudden withdrawal of a body part which comes in contact with objects that are extremely hot, cold pointed or animals that are poisonous. The reflex pathway consists of one afferent neuron (receptor) and one efferent (effector or excitor) neuron arranged in a series.

The afferent neuron receives signal from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS (at the level of spinal cord). The efferent nueuron carries signals from CNS to the effector. The stimulus and response thus forms a reflex arc in the knee jerk reflex.

Sensory Reception And Processing
The sensory organs detect all types of changes in the environment and sent to different parts/centres of the brain. The sense organs are the eye (sensory organ for vision) and the ear (sensory organ for hearing).

Eye
Our paired eyes are located in sockets of the skull called orbits.

Parts of an eye
The wall of the eye ball is composed of three layers. External layer is composed of a dense connective tissue and is called the sclera. Anterior portion of this layer is called the cornea. Middle layer, choroid, contains many blood vessels and looks bluish in colour.

The choroid layer is thin over the posterior part of eye ball, but it becomes thick in the anterior part to form the ciliary body. The ciliary continues forward to form a pigmented and opaque structure called the iris which is the visible coloured portion ofthe eye.

1. The eye ball contains lens which is held in place by ligaments attached to the ciliary body. In front of the lens, the aperture surrounded by the iris is called the pupil.
2. The inner layer is the retina contains three layers of cells – from inside to outside.
3. Ganglion cells, bipolar cells and photoreceptor cells.
4. There are two typ es of photoreceptor cells, namely, rods and cones
5. The daylight (photopic) vision and colour vision are functions of cones
6. The twilight (scotopic) vision is the function of the rods.
7. The rods contain a purplish-red protein called the rhodopsin which contains a derivative of Vitamin A. In the human eye, there are three types of cones that respond to red, green and blue lights.

What is blind spot?
The optic nerves and the retinal blood vessels enter above the posterior pole of the eye ball. Photoreceptor cells are not present in that region and hence it is called the blind spot.

What is macula lutea?
At the posterior pole of the eye lateral to the blind spot, there is a yellowish pigmented spot called macula lutea with a central pit called the fovea where only the cones are densely packed. It is the point where the visual acuity (resolution) is the greatest.

The space between the cornea and the lens is called the aqueous chamber and contains fluid called aqueous humor. The space between the lens and the retina is called the vitreous chamber and contains fluid called vitreous humor.

Mechanism of Vision
The light rays falls on the retina through cornea and lens generate impulses in rods and cones. The photosensitive compounds (photopigments) in the human eyes is composed of opsin (a protein) and retinal (an aldehyde of vitamin A). Light induces the changes in the structure of the opsin.

This causes membrane permeability changes. As a result, potential differences are generated in the photoreceptor cells. This produces a signal that generates action potentials in the ganglion cells through the bipolar cells.

These action potentials are transmitted by the optic nerves to the visual cortex area of the brain, where the neural impulses are analysed and the image formed on the retina is recognised based on earlier memory and experience.

The Ear
The ear is divided into three major sections called the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and external auditory meatus (canal).The pinna collects the vibrations of sound. The external auditory meatus leads inwards and extends up to the tympanic membrane (the ear drum).

There are wax-secreting sebaceous glands in the skin of the pinna and the meatus. The middle ear contains three ossicles called malleus, incus and stapes which are attached to one another in a chain-like fashion.

The malleus is attached to the tympanic membrane and the stapes is attached to the oval window. of the cochlea. The ear ossicles increase the efficiency of transmission of sound waves to the inner ear.

An Eustachian tube connects the middle ear cavity with the pharynx. The Eustachian tube helps in equalising the pressures on either sides of the eardrum. The fluid-filled inner ear called labyrinth consists of two parts, the bony and the membranous labyrinths.

The bony labyrinth is connected with membranous labyrinth, which is surrounded by a fluid called perilymph. The membranous labyrinth is filled with a fluid called endolymph. The coiled portion of the labyrinth is called cochlea.

The membranes constituting cochlea, the reissner’s and basilar, divide the surounding perilymph filled bony labyrinth into an upper scala vestibuli and a lower scala tympani. The space within cochlea called scala media is filled with endolymph.

At the base of the cochlea, the scala vestibuli ends at the oval window The organ of corti is a structure located on the basilar membrane which contains hair cells that act as auditory receptors. The hair cells are present in rows on the internal side of the organ of corti.

The basal end of the hair cell is in close contact with the afferent nerve fibres. A large number of processes called stereo cilia are projected from the apical part of each hair cell. Above the rows of the hair cells is a thin elastic membrane called tectorial membrane. The inner ear also contains vestibular apparatus, located above the cochlea.

The vestibular apparatus is composed of three semi-circular canals and the otolith organ consisting of the saccule and utricle. The membranous canals are suspended in the perilymph of the bony canals. The base of canals is swollen and is called ampulla, which contains a projecting ridge called crista ampullaris which has hair cells.

The saccule and utricle contain a projecting ridge called macula. The crista and macula are the specific receptors of the vestibular apparatus responsible for maintenance of balance of the body and posture.

Mechanism of Hearing
How does ear convert sound waves into neural impulses, which are sensed and processed by the brain enabling us to recognise a sound?
The external ear receives sound waves and directs them to the ear drum.The ear drum vibrates in response to the sound waves and these vibrations are transmitted through the ear ossicles (malleus, incus and stapes) to the oval window.

The vibrations are passed through the oval window on to the fluid of the cochlea, where they generate waves in the lymphs. The waves in the lymphs induce a ripple in the basilar membrane. These movements of the basilar membrane bend the hair ceils, pressing them against the tectorial membrane.

As a result, nerve impulses are generated in the associated afferent neurons. These impulses are transmitted by the afferent fibres via auditory nerves to the auditory cortex of the brain, where the impulses are analysed and the sound is recognized.

The vibrations are passed through the oval window on to the fluid of the cochlea, where they generate waves in the lymphs. The waves in the lymphs induce a ripple in the basilar membrane. These movements of the basilar membrane bend the hair cells, pressing them against the tectorial membrane.

As a result, nerve impulses are generated in the associated afferent neurons. These impulses are transmitted by the afferent fibres via auditory nerves to the auditory cortex of the brain, where the impulses are analysed and the sound is recognized.

NCERT SUPPLEMENTARY SYLLABUS
Sense organs:
The environmental changes (both internal and external) called stimuli detected by the special sensory cells, are conveyed to the brain in the form of nerve impulses. The response for each stimulus from brain is sent to the various body parts for its well being. There are five senses: touch, vision, hearing, smell and taste.

While touch is a complex general sense, the other four are special senses. The general sensory receptors are simple receptors that are present in the skin, mucous membranes, connective tissues and muscles.

These sense the information such as tactile sensation (a mix of touch, pressure, stretch and vibration), heat, cold, pain and muscle sense.

Special sensory receptors are present in the head especially sensory organs like eyes and ears and tissues of the taste buds and olfactory epithelium. These sensory organs and tissues of eye and ear are photoreceptors and the auditory receptors respectively.

The chemical senses: the taste and smell:
The receptors fortaste and smell are called as chemoreceptors found as film of liquid coating in the membranes of the receptor cells. The taste receptors are specialized cells that detect chemicals present in the mouth while smell receptors are modified sensory neurons in the nasal passage which detect the volatile chemicals.

These two types of receptors complement each other and often respond to the same stimulus. The smell receptors are 3,400 times more sensitive than the taste receptors.

Sense of smell (olfaction):
Nose contains the receptors of smell, in the mucous coated thin, yellowish patch (about 5 cm2) of modified pseudo stratified epithelium called olfactory epithelium. It is located at the roof of the nasal cavity on either sides of the nasal septum.

The olfactory epithelium contains three types of cells:

• millions of olfactory receptor cells
• columnar supportive cells
• short basal cells.

Olfactory receptors bear a cluster of about 20 modified cilia which function as receptor sites. These cilia extend from the olfactory epithelium into the thin coat of nasal mucous secreted by the supportive cells and olfactory glands. This mucous dissolves the airborne odour molecules.

Once dissolved, the chemicals bind to the specific receptors on the cilia stimulating the receptor cells. This causes depolarization then action potential in the receptor cell.

The axons of the olfactory receptors unite to form the olfactory nerve which transmits the information directly to olfactory bulb, a relay station in the brain. The nasal cavity contains pain receptors that respond to irritants such as ammonia, vinegar or hot chilly pepper.

Impulses from these pain receptors reach the brain. The brain combines these sensations with those of smell to identify the odours Humans can detect about 10,000 different odours but the olfactory capability of fish and mammals such as a dog is high.

Sense of taste (gustation):
The receptor cells fortaste are located in taste buds. Humans have about 10,000 taste buds are located in pockets around the papillae on the surface and sides of the tongue, but some on the surface of the pharynx and the larynx.

Each taste bud contains about 40 specialized receptor cells or gustatory cells, that helps to replace the worn out cells of the taste buds. The receptor cells for taste are not neurons, but they are microvilli .The microvilli protrude into the surrounding fluids through a narrow opening called the taste pore.

Dissolved chemicals contacting the microvilli bind to specific receptor proteins on the microvilli, thereby depolarizing the cell,it releases neurotransmitter which leads to the generation of an action potential in the associated sensory neuron.

Each dendrite receives signals from several receptor cells within the taste bud pass to the brain stem. From here the nerve impulse is relayed to the taste centre in the cerebral cortex of the brain that perceives the taste sensation.
In humans there are four basic taste senses:

Sense of touch:
Skin is the largest sense organ. These sensations of touch come from millions of microscopic simple sensory receptors located all over the skin and associated with the general sensations of contact or pressure, heat, cold, and pain. Some parts of the body have a large number of these such as the fingertips.

Structurally, these touch receptors are either free dendritic endings or encapsulated dendritic endings present in the skin (and other parts of the body). Free or bare dendritic nerve endings are present throughout the epidermis in “zigzag” form .These respond chiefly to pain and temperature but some respond to pressure as well.

Whenever one or more of these sensory receptors are stimulated (by heat, cold, vibrations, pressure or pain) an impulse or action potential is generated. This impulse is then taken to the spinal cord and from there to the brain which analyses the stimulus and then generates appropriate response.

Students can Download Chapter 7 Bill of Exchange Notes, Plus One Accountancy Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Accountancy Notes Chapter 7 Bill of Exchange

Summary:
Bill of Exchange:
A bill of exchange is an acknowledgement of debt given by one person to another, incorporating all the terms and conditions of payment.

Features and advantages of a bill:
A bill is a written unconditional order, it is signed by the creditor and accepted by the debtor, the amount of the bill is payable either on demand or at a fixed period.

Parties to a bill of Exchange:
There are three parties, ie., drawer, drawee and payee.

Promissory Note:
A promissory note is an undertaking in writting given by the debtor to the creditor to pay the latter a certain sum of money in accordance with the conditions stated therein. There are two parties to a promissory note, the promissor and the promisee.

Maturity of Bill:
The term maturity refers to the date on which a bill or promissory note becomes due for payment. In arriving at the maturity date three days known as “days of grace” must be added to the date on which the period of credit expires instrument is payable.

Endorsement:
An endorsement is a written order on the back of the instrument by the payee or the holder for transferring his right to another person.

Accounting treatment:
A bill can be treated in the following four ways by its receiver.

Dishonour of a bill:
A bill is said to have been dishonoured when the drawee fails to make the payment on the date of maturity. In this situation, liability of the acceptor is restored. Therefore, the entries made on the receipt of the bill should be reserved. The entries of dishonour of bill as follows
(i) When the bill was kept by drawer till maturity.

Noting Charges:
When a bill is dishonoured due to non-payment, it is usual to get it ‘noted’, to establish the matter of dishonour. The noting is done by “Notary Public.” Noting authenticates the fact of dishonour. For providing this service, a fees is charged by the Notary Public which is called Noting Charges. The following facts are generally noted by the Notary;

• Date, fact and reasons of dishonour;
• If the bill is not expressly dishonoured, the reasons why he treats it as dishonoured and;
• The amount of noting charges.

The entries recorded for noting charges in the drawers book are as follows:
When Drawer himself pays:

Where endorsee pays:

When the bank pays on discounted bill:

When the bank pays in the event of sending the bill for collection to the bank:

The entry recorded for noting charges in the book of drawee as follows:
For recording noting charges the drawee opens “Noting ChargesAccount”.

Renewal of the bill:
Sometimes the acceptor of the bill foresees that it may be difficult to meet the obligation of the bill on maturity and may, therefore approach the drawer with the request for extension of time for payment.

If it is so, the old bill is cancelled and . the fresh bill with new terms of payment is drawn and duly accepted and delivered. This is called renewal of the bill. The drawee may have to pay interest to the drawer for the extended period of credit.
Following journal entries are recorded in the case of renewal of the bill.

Retiring of the Bill:
Making payment of the bill of exchange before the due date is called retiring of the bill. To encourage the retirement of the bill, the holder allows some discount called “Rebate on bill” for the period between date of retirement and maturity. The rebate is calculated at a certain rate of interest.

The following journal entries are recorded:
(i) In the book of drawer:
On retiring the acceptance, rebate allowed.

(ii) In the book of drawee:

Students can Download Chapter 9 Locomotion and Movement Notes, Plus One Zoology Notes helps you to revise the complete Kerala State Syllabus and score more marks in your examinations.

Kerala Plus One Zoology Notes Chapter 9 Locomotion and Movement

What is locomotion?
The movements result in a change of place or location. Such voluntary movements are called locomotion. Walking, running, climbing, flying, swimming are all some forms of locomotory movements.

Locomotory Movements In Lower Organisms

1. Paramoecium, cilia helps in the movement of food through cytopharynx and locomotion.
2. Hydra use its tentacles for capturing its prey and also use them for locomotion.

All locomotions are movements but all movements are not locomotions.

Types Of Movement
The three main types of movements of cells of the human body are

• Amoeboid
• Ciliary
• Muscular.

Muscle
About 40-50 perent of the body weight of a human adult is contributed by muscles. Muscles are classified based on their location, three types of muscles are identified.

1. Skeletal
2. Visceral
3. Cardiac.

1. Skeletal muscles:
They have a striped appearance and called as striated muscles. They are voluntary muscles because their activities are under the voluntary control of the nervous system. They are involved in locomotory actions and changes of body postures.

2. Visceral muscles:

• They are located in the innerwalls alimentary canal, reproductive tract, etc. They are called smooth muscles (non striated muscle).
• Their activities are not underthe voluntary controlcalled as involuntary muscles.
• They helps in transportation of food through the digestive tract and gametes through the genital tract.

3. Cardiac muscles:

• They are found in the muscles of heart. Based on appearance, cardiac muscles are striated and involuntary.
• Skeletal muscle is made of a number of muscle bundles or fascicles held together by a common collagenous connective tissue layer called fascia
• Each muscle bundle contains a number of muscle fibres. Each muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm.
• Muscle fibre is a syncitium because it contains many nuclei.
• The endoplasmic reticulum, i.e., sarcoplasmic reticulum of the muscle fibres is the store house of calcium ions.

Structure of Contractile Proteins
Each actin filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.

Acomplex protein Troponin is distributed at regular intervals on the tropomyosin. In the resting state a subunit of troponin masks the active binding sites for myosin on the actin filaments.

Monomeric proteins called Meromyosins forms one thick filament. Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.

Mechanism of Muscle Contraction
The sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.
Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate.

1. In the junction, the neurotransmitter (Acetyl choline) is released which generates an action potential in the sarcolemma. This spreads and release of calcium ions into the sarcoplasm.
2. Increase in Ca⁺⁺ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.
3. The energy from ATP hydrolysis is used to bind the myosin head with exposed active sites on actin to form a cross bridge.
4. This pulls the attached actin filaments towards the centre of ‘A’ band. The Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e. contraction.
5. During shortening of the muscle the T bands get reduced, whereas the ‘A’ bands retain the length The myosin, releasing the ADP and P1 goes back to its relaxed state.
6. The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and breakage is repeated causing further sliding.
7. The process continues till the Ca⁺⁺ ions are pumped back to the sarcoplasmic cisternae resulting in the masking of actin filaments.

This causes the return of ‘Z’ lines back to their original position, i.e., relaxation.

What is muscle fatigue?
Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen causing fatigue. Muscle contains a red coloured oxygen storing pigment called myoglobin. These muscles contain plenty of mitochondria which helps in ATP production.

Hence they are called aerobic muscles. Some of the muscles possess very less quantity of myoglobin and gives whitish appearance . These are the White fibres. Number of mitochondria are also few in them. They depend on anaerobic process for energy.

Seletal System
1. Skeletal system consists of a framework of bones and a few cartilages.

2. Bone and cartilage are specialised connective tissues.

3. The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts. In human beings, this system is made up of 206 bones and a few cartilages. It is grouped into two divisions.

Axial skeleton:

1. It comprises 80 bones distributed along the main axis of the body.
2. The skull, vertebral column, sternum and ribs constitute axial skeleton.

The skull is composed of two sets of bones – Cranial bones are 8 in number. The facial region is made up of 14 skeletal elements which form the front part of the skull.

Diagrammatic view of human skull:
A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull.

What is ear ossicles ?
Each middle ear contains three tiny bones – Malleus, Incus and Stapes, collectively called Ear Ossicles.

Vertebral column:
It is formed by 26 serially arranged units called vertebrae and is dorsally placed. Each vertebra has a central hollow portion (neural canal) through which the spinal cord passes. First vertebra is the atlas and it articulates with the occipital condyles. The vertebral column is differentiated into cervical (7), thoracic (12), lumbar (5), sacral (1-fused)and coccygeal (1-fused) regions starting from the skull.

Vertebral column (right lateral view) Ribs and rib cage. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.

Sternum:
It is a flat bone on the ventral midline of thorax.
There are 12 pairs of ribs.
1. First seven pairs of ribs are called true ribs. Dorsaily, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage.

2. The 8^th, 9^th and 10^th pairs of ribs do not articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called vertebrochondral (false) ribs.

3. Last 2 pairs (11^th and 12^th) of ribs are not connected ventrally and are called floating ribs. Thoracic vertebrae, ribs and sternum together form the rib cage.

Appendicular skeleton:
It includes bones of the limbs alongwith their girdles Each limb is made of 30 bones. The bones of the hand (fore limb) are humerus, radius and ulna, carpals (wrist bones-8 in number), metacarpals (palm bones – 5 in number) and phalanges (digits – 14 in number) Femur (thigh bone – the longest bone), tibia and fibula, tarsals (ankle bones – 7 in number), metatarsals (5 in number) and phalanges (digits -14 in number) are the bones of the legs (hind limb).

A cup shaped bone called patella cover the knee ventrally (knee cap). Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton.

Each half of pectoral girdle consists of a clavicle and a scapula. Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh ribs. The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion.

Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint. Each clavicle is a long slender bone with two curvatures. This bone is commonly called the collar bone. Pelvic girdle consists of two coxal bones Each coxal bone is formed by the fusion of three bones

1. ilium
2. ischium
3. pubis.

Joints
Joints are points of contact between bones, or between bones and cartilages. The movability of joints vary depending on different factors.
Joints are classified into three,

Disorders Of Muscular And Skeletal System
Myasthenia gravis:
Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.

Muscular dystrophy:
Progressive degeneration of skeletal muscle mostly due to genetic disorder.

Tetany:
Rapid spasms (wild contractions) in muscle due to low Ca⁺⁺ in body fluid.

Arthritis:
Inflammation of joints.

Osteoporosis:
Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause.

Gout:
Inflammation of joints due to accumulation of uric acid crystals.

NCERT SUPPLEMENTARY SYLLABUS
Types of movements: Flagellar movement
The three main types of movements shown by the cells of the human body are amoeboid, ciliary and muscular. Human sperms shows type of movement called the flagellar movement. The flagellum is the propulsion equipment (due to whip like movement of the tail and the middle piece of the sperm) forthe movement of sperm towards the ovum.