1styear BIOLOGY Notes Chapter-4

Chapter-4
THE CELL

CELL
It is the basic structural and functional unit of life, which is able to carry out all the life processes.

CELL THEORY
The cell theory was collectively proposed by “Schleiden(1838), Schawnn(1839) and Virchow (1858).

IMPORTANT POSTULATES
The fundamental points of the cell theory are:
(a) The cell is the structural and functional unit of all living organism.
(b) All organisms are composed of one or more cells.
(c) New cells can arise only by division of pre-existing cells.
Thus cell theory established the concept that the function of an organism is the result of activities and interaction of the cell units.

MICROSCOPE
DEFINITION
An instrument with the help of which we see small, tiny and minute objects which can’t be observe by naked human eye.

TYPES OF MICROSCOPE
There are three main types of microscope.

1. LIGHT MICRO SCOPE
In this microscope visible light is used as source of illumination.

2. X-RAY MICROSCOPE
X-Rays are used as source of illumination.

3. ELECTRON MICROSCOPE
Electron beam is used as source of illumination.

There are further two sub-types of electron microscope which are:

(A)TRANSMISSION ELECTRON MICROSCOPE
In this type resultant image is obtained on a fluorescent screen or photographic film.

(B)SCANNING ELECTRON MICROSCOPE
In this type resultant image is obtained on a television screen.

MAGNIFICATION OF MICROSCOPE
Ability of microscope to increase the shape and size of the objects image. It can be calculated by multiplying the power of its eye pieces with its magnifying power of its objective.

RESOLUTION OF MICROSCOPE
The capacity of microscope to separate adjacent forms or object. Also known as “Minimum Resolved Distance”.

CONTRAST
It is important to distinguishing one part of cell from another.
• Difference between light and electron microscope
• Prokaryotes and eukaryotes

CELL MEMBRANE
Each cell is covered by an asymmetrical, porous, thin, semi permeable sheet called cell membrane or plasmalemma.

CHARACTERISTICS OF CELL MEMBRANE
Living part of the cell, consist of lipid + protein.
• 1.5 micron in thickness.
• Consist of two layers of lipid.
• Lipid of plasma membrane are,

1. Phospho-lipids
2. Glycolipids
3. Sterol
4. Cholesterol.

STRUCTURE OF CELL MEMBRANE
Cell membrane made up of phospho-lipids bilayer and each layer consists of ,
1. Head (hydrophilic end)
2. Tail (hydrophobic end)

HEAD (HYDROPHILIC/POLAR END)
Present towards the surface and formed of phosphates.

TAIL (HYDROPHOBIC/NON-POLAR END)
Present towards the center and formed of fatty acids.
The non-polar ends of phospho lipids face each other, whereas their polar ends are in association with protein or carbohydrates between every two phospo lipids molecule lies a molecule of “Cholesterol”.

FLUID MOSAIC MODEL
INTRODUCTION
The fluid mosaic, bilayer model was proposed by “Singer and Nicolson (1972).

POSTULATES OF FLUID MOSAIC MODEL
Important postulates of this model are,
(a) The cell membrane consists of lipid bilayer, in which a variety of proteins are present.
(b) These proteins float in the fluid matrix of lipid (as ice bergs in the sea)

ARRANGEMENT OF PROTEINS
According to the fluid mosaic model proteins are:

1. INTRINSIC/INTEGRAL PROTEINS
These proteins peneterate the membrane surface and enter the lipid layers (partially or wholly)

2. EXTRINSIC/PERIPHERAL PROTEINS
These are located adjacent to outer and inner surface of membrane and float like ice-berg in the sea.

ARRANGEMENT OF LIPIDS
The non-polar end face each other while their polar ends are towards the surface.

SIGNIFICANCE OF MODEL
• Cell membrane is flexible.
• Can change shape (because the protein and lipid of the membrane can move).

FUNCTION OF MEMBRANE PROTEIN
• Certain proteins themselves act as enzymes.
• Some protein act as carrier for active transport.
• Provide elasticity to membrane.
• Pores are lined by the proteins.

FUNCTION OF LIPIDS PRESENT IN MEMBRANE
• The lipids give rigidity to cell membrane.
• They lower the surface tension.

FUNCTIONS OF CELL MEMBRANE
• It performs the two main function.
• Protection of Protoplasm.
• Regulation of material (In and Out of cell) through its permeabality.

PERMEABILITY OF MEMBRANE
The permeability of membrane is regulated by two processes.
(1) Passive Transport (Osmosis and Diffusion)
(2) Active Transport (Endocytosis, Exocytosis)

1. PASSIVE TRANSPORT
Such type of molecules transport which does not require energy. It is further divided into,

DIFFUSION
Spreading and free movement of molecules (or ions) from the region of higher concentration to the region of lower concentration (till equilibrium state)

SIGNIFICANCE
• Movement of oxygen and digested food (glucose, amino acids, fatty acids) into the cell.
• Movement of excretory waste out of cell.

OSMOSIS
Diffusion of water by semipermeable membrane or the movement of solvent molecules from higher to lower concentration across semi permeable membrane.

SIGNIFICANCE
• Liquids, primarily water molecules enter and leave the cell by Osmosis.
• It helps to maintain a balance (osmotic pressure) in and out of cell.

2. ACTIVE TRANSPORT
Such type of molecule transport which require energy. Or Movement of molecules against the concentration by the expenditure of energy through a carrier (i.e. movement of molecules from the region of lower concentration to higher concentration by protein using ATP as energy.

SIGNIFICANCE
Absorption of excess food (glucose), ions (K+ and Na+) takes place by Active transport.

CONDITIONS
• It is unidirectional.
• ATP provides energy.
• Protein act as carrier.

Active transport is further subdivided into,
(1) Phagocytosis and Pinocytosis (Endocytosis).
(2) Exocytosis.

PHAGOCYTOSIS
Process of picking and ingestion of large solid particle by plasma membrane (which can not enter by diffusion, osmosis or active transport).

SIGNIFICANCE
• Ingestion of solid food particles.
• WBCs pick foreign particles (certain bacteria)

PINOCYTOSIS
Process of fluid intake, for absorbing fluid by forming pinocytic vesicle (the fluid which cannot be absorbed by osmosis, enters through it)

SIGNIFICANCE
Helps in absorption of harmones, lipids etc.

CELL WALL
The cell wall is the outer most covering of a plant cell. It is composed of cellulose (a carbohydrate) and some other chemical substances.
This hard covering gives form, firmness and strength to the plant cell.
In a young cell it is thin and delicate but in a mature cell it becomes thick due to the deposition of various chemical substances on its inner surface.
There are three layer of cell wall.

1. MIDDLE (LAMELLA)
• First formed cell plate.
• Cementing layer between two daughter cells.
• Composed of Ca++ and Mg++ pectate.
• ells are separated when this layer is dissolved.

2. PRIMARY WALL
• First product of cell synthesized by protoplast.
• In young cells it is thin and elastic while it becomes thick and rigid on maturity.
• Made up of Hemicellulose (50%), cellulose (25%) and pectate substances.

3. SECONDARY WALL
• Composed of cellulose.
• Present inside the primary wall.
• Can be modified through the deposition of lignin and other substances.

NUCLEUS
It control all the activities of the cell and was discovered by Robert Brown in 1831.

It consist of the following parts,
(1) Nuclear Membrane.
(2) Nucleoplasm or Karyoplasm.
(3) Nucleolus.
(4) Chromatin Network.

1. NUCLEAR MEMBRANE
The nucleus is bounded by a double layered membrane which bears pores and is known as “Nuclear Membrane”

2. NUCLEOPLASM
Inside the nuclear membrane is a structure less fluid called “Nucleoplasm” and highly rich with proteins.

3. NUCLEOLUS
It is a patch work of granules rich in R.N.A formed in the nucleus. They may be more than one in a single nucleus. It contains mRNA formed from DNA, later mRNA comes out of nucleus to control protein formation.

4. CHROMATIN NETWORK
There is a network of threads dispersed in the karyoplasm called (Chromatin network)
Each individual thread is called (Chromosomes).
These are made up of DNA and are carrier of genes.


MEMBRANE BOUND ORGANELLES
(1) ENDOPLASMIC RETUCULUM
It is a complex series of tubules in the cytoplasm. Endoplasmic reticulum are of two types,
(1) Agranular or Smooth EPR.
(2) Granular or Rough EPR.

SMOOTH EPR
• It has no attached ribosome’s.
• Function is to synthesis lipid.

ROUGH EPR
• It has ribosome’s attached to its outer surface.
• Synthesize protein and also transport material within the cell.

(2) MITOCHONDRIA
An oval body bounded by a double membrane. The inner membrane is folded to form shelves/incomplete partitions. Which are known as “Crista”, here oxidative enzyme are present. They are sites for aerobic cellular respiration and the energy is produced. Therefore also known as “Power house of cell”

(3) GOLGI APPARATUS(DICTYOSOMES)
These are thin, plate like structures and are usually located near the nucleus. These are the site of formation of lysosomes and also conjugate protein, modify structure of substances, synthesized by EPR to form lysosomes and secretary vesides. Golgi bodies of plants and lower animals (mostly invertebrates) are known as “Dictyosomes”.

(4) LYSOSOMES
They are large, some what irregular structure formed in the cytoplasm formed by golgi-bodies. They contain hydrolytic enzymes which destroys foreign particles. They are also known as “Suicide Sacs” because after secreting the enzymes they digese their own proteins (Autophagy).
NOTE: (Lysosomal Storage Diseases )

(5) PLASTIDS
They are specialized organelles of plant cell that contain pigment or they synthesize reserve substances.
They are of three kinds,

(A) LEUKOPLAST
leuco = white
Leukoplast are colourless and store nutrient material.

(B)CHLOROPLAST
Chloroplast are green having chlorophyll that performs photosynthesis.

(C) CHROMOPLAST
Chromo = Colour
Chromoplast contain different coloured (red, yellow, orange or other than green) pigments. They are found in the cells of different coloured flowers and fruits.

(6) MICRO BODIES
It includes peroxisome and glyoxysome.

(A) PEROXISOME
These are the single membrane bounded microbodies contain enzymes for transferring hydrogen atom to oxygen i.e. forming hydrogen peroxide.
• Hydrogen peroxide is very toxic to the cell therefore it is immediately break down to water by enzyme catalyst.
• These microbodies help in detoxyfication of alcohal and mostly present in liver cells.

(B) GLYOXYSOME
• It is a single layered membrane bound structure containing enzymes which metabolize some molecules in photosynthesis and respiration.
• They also cause oxidation of fatty acids.

CYTOSKELETON
Cytoskeleton means skeleton of the cell, which is mostly composed of microtubules, microfilaments and intermediate filaments.

(A) MICRO TUBULES
• Microtubules are hollow cylinders with an outerdiameter of 25nm.
• They are made up of a special type of globular protein tubulin.
• In single microtubule consist of hundredth of thousands of tubulin sub units, which are usually arranged in 13 columns called Protofilaments.
• Microtubules are arranged in assemble and disassemble manner.
• In animal cells and lower plants they also form centriole, cilia and flagella.

(B) MICROFILAMENTS
• Microfilaments are solid structures, thread like with a diameter of 7nm.
• They are also composed of globular proteins.
• Each microfilament consist of two actin (Protein) chains that inter wing in a helical fashion.

(C) INTERMEDIATE FILAMENTS
• They are intermediate in size having a diameter of 8nm to 11nm.
• They are rope like polymers of Fibrous protein.
• In skin and hair these filaments are made up of protein keratin.
• They provide mechanical strength to the cell and support the nuclear envelope.

NON MEMBRANE BOUND CYTOPLASMIC ORGENELLE
(1)RIBOSOMES
• These are small structures concerned with protein synthesis in all type of the cells i.e. Prokaryotic as well as Eukaryote.
• They are freely dispersed in cytoplasm of Prokaryotic cell but in Eukaryotic cells they may be free or attached with endoplasmic reticulum.
• More than 50 type of proteins are present in ribosome structure and they contain high quantity of RNA.
• Under the direction of Nucleus ribosome produce the protein made it by the cell.
• Each Ribosome consist of two unequal parts.
• These are the smallest and most vital cellular components, manufactured in the nucleolus.

(2) CENTRIOLE
• They are only present in animal cells and certain lower plants.
• Mostly near the nucleus.
• Each centriole consist of two cylinders lying perpendicular to one another.
• Each cylinder consist of nine parallel triplets of hollow cylindrical microtubules.
• During the cell division they replicate and move towards opposite poles of the cell.
• In mitosis and meiosis they form thread like fibers which rediate from each centriole are known as mitotic apparatus.

(3)VACUOLES
• These are non-protoplasmic fluid filled cavities in the cytoplasm.
• Their membrane is known as Tonoplast.
• They are more prominent in mature cells.
• In plant cells vacuoles are filled with cell sap and act as store, house.
• They also play an important role in plant defence.
• In animal cells vacuole contain hydrolytic enzymes (i.e. lysosomes)

1styear BIOLOGY Notes Chapter-3

Chapter-3
ENZYMES

ENZYMES(BIO-CATALYSTS)
Enzymes are bio-catalyst which speed up the chemical reactions by lowering “Energy of activation”.



ENERGY OF ACTIVATION
Amount of energy which is required to start a chemical reaction. OR Energy required to break a (particular covalent) bond present in reactant.

NOMENCLATURE OF ENZYMES
Enzyme is a Greek word means-En(in) and Zyme(yeast).

DISCOVERY OF ENZYME
Term “Enzyme” was coined by F.W Kuhne in 1978.

NATURE OF ENZYME
Almost all enzymes are protein in nature except few which are nitrogenous acids like RNA-DNA(Ribozymes). Ribozymes catalyze reactions in genetic informations.

CHARACTERISTICS OF ENZYMES
• Protein in nature and are formed by living cells.
• May be intracellular or extra cellular.
• Remains unchanged during and after the reaction.
• Speed up the rate of reaction by decreasing energy of action.
• Specific in their nature.
• Heat sensitive and act on particular (optimum) temp.
• Each has specific substrate pH for its activity.
• Action can be alter by activators and inhibitors.

CLASSIFICATION OF ENZYME (ON THE BASIS OF STRUCTURE)
Pure or Simple Enzyme consist of only protein (e.g.Amylase and Pepsin) Conjugated or Holoenzymes: May contain a non-protein part “Prosthetic group” as well (e.g. Phosphatase and Peptidase)
Holoenzyme = Apoenzyme + Prosthetic group
................(Protein part)....(Non-protein part)



CLASSIFICATION OF ENZYME (ON THE BASIS OF FUNCTIONS)
(1) OXIDOREDUCTASE
Catalyze reactions in which one substrate is oxidized while other is reduced. Sub classes are:
• Dehydrogenases(convert single bond to double bond)
• Oxidases (use oxygen as oxidant)
• Peroxidases (use H202 as oxidant)
• Hydroxylases (introduce hydroxyl group)
• Oxygenases (introduce mol. Oxygen in place of double bond).

(2) TRANSFERASES
Transfer one carbon group (e.g. methyl) from one substrate to another substrate.

(3) HYDROLASES
Catalyze hydrolytic cleavage of C-O, C-N, C-C and P-O bonds and other single bonds (e.g. Peptidases, Esterases, Glycosidases and Phosphatidases).

(4) LYASES
Catalyze Elimination reactions to form double bond and reversible reaction by adding groups across double bond (e.g. Decarboxlases, Aldolases and Dehydratases).

(5) ISOMERASES
They alter the structure but not the atomic composition by moving a group from one position to another in one molecule (e.g. Epimerases, Mutases).

(6) LIGASES
Catalyze reaction in which two molecules are joined. They are also known as synthtases.

ROLE OF ENZYME
The enzyme react with (energy rich or energy poor) molecules and forms an intermediate complex that breaks into,
(a) Product
(b) Enzyme

(i) Substrate + Enzyme = Complex
(ii) Complex = Product + Enzyme
The equilibrium is achieved if the ratio of conc of reactants (substrate) and product remains same.
Rate of reaction 1/µ Energy of activation

MODE OF ACTION OF ENZYMES
1- The action of enzyme depends on its chemical structure. A typical enzyme molecule, has “3D” structure.
2- Has depression or pit for substrate (to fit in) known as “Active site”.
3- Any other site other than active site is called “Allosteric site”
There are two theories in respect of enzyme action, which are as follows.

LOCK AND KEY MODEL
Proposed by Fischer (1898) and modified by Paul Filder and D.D Woods according to this model,
• The active site of enzyme has distinct shape.
• It allows few substrate to fit in (like a particular lock allows particular key to fit in)
• Enzyme breaks substrate to product
FIGURE From Text Book 3.3 page #46 (The cycle of Enzyme - substrate Interaction)

INDUCE FIT MODEL
Proposed by koshland (1959), it states that
• Enzyme binds with a substrate
• This binding induce changes in enzyme structure
• Due to this change enzyme acts and forms product

FACTORS AFFECTING ENZYME ACTIVITY
The activity of enzymes depend on following factors,

1. SUBSTRATE CONCENTRATION
• Increases with increase in substrate concentration (up to a limit)
• At very high concentration, activity again decreases due to saturation of enzyme with substrate and saturation of product i.e. higher concentration of product.

2. TEMPERATURE
• Increases with in temperature(up to limits)
• Maximum activity at optimum temperature.
• Highly active at 37°C and destroyed at 100°C
• At 0°C minimum activity.

3. PH
Enzymes are pH specific i.e. work in specific pH(because of protein can act both in acidic and basic medium.

4. WATER
Enzyme activity is usually maximum (up to limits) but decrease after limits (dilution of enzyme)

5. RADIATIONS
Enzymes become inactive due to radiations (including Alpha, Beta, Gamma rays).

6. CO-ENZYME AND ACTIVATORS
Induce the enzyme activity.

THINGS TO BE REMEMBER
INHIBITORS
Substances which decreases the activity of enzymes.

COMPETITIVE INHIBITORS
Inhibitor molecules which resemble the normal substrate molecule and compete for admission into the active site. They block the substrate from entering active site.

NON-COMPETITIVE INHIBITORS
Inhibitors bind to a part of the enzymes away from the active site (Allosteric site). This binding cause change in the enzyme molecule shape and decrease in enzyme activity.

FEED BACK INHIBITION
Common biological control mechanism of brain in order to regulate enzyme activity.

PROSTHETIC GROUP
Non-protein part of enzyme (Co-enzyme or Co-factor)

CO-ENZYME
When prosthetic group consist of organic molecules (like FAD/NAD)

CO-FACTORS/ACTIVATORS
When prosthetic group consist of inorganic molecules (like Ca++, Na+ etc).

APOENZYME
Protein part of enzyme.

1styear BIOLOGY Notes Chapter-2

Chapter-2
BIOLOGICAL MOLECULES

BIOCHEMISRTY
Biochemistry is a branch of biology, which deals with the study of chemical components and chemical processes in living organisms.

WATER (H2O)
MAIN CHARACTERISTICS OF WATER
• Chemically it is “Dihydrogen oxide”
• It is the most abundant component in living cell.
• Its amount varies approximately from 70 to 90% and life activities occur in the cell due to the presence of water.
• It is a polar molecule, means that it has a very slightly negative end (the oxygen atom) and a very slightly positive end (the hydrogen atom).
• Due to its polarity, H2O molecules form hydrogen bonds.

IMPORTANT BIOLOGICAL PROPERTIES OF WATER
(1) BEST SOLVENT
• Water is an excellent solvent for polar substances, when ionic substances dissolved in water, dissociate into positive and negative ions.
• Non-ionic substances, having charged groups in their molecules, are dispersed in water.
• Because of solvent property of water, almost all reactions in cells occur in aqueous media.
(2) HIGH HEAT CAPACITY
• Water has great ability of absorbing heat due to its high specific heat capacity.
• The specific heat capacity of water is the number of calories required to raise the temperature of 1g water through 1ºC.
• The thermal stability plays an important role in water based protoplasm of individual’s metabolic activities.
(3) HIGH HEAT OF VAPORIZATION
• Liquid water requires higher amount of heat energy to change into vapours due to hydrogen bonding which holds the water molecules together.
• It provides cooling effect to plants when water is transpired, or to animals when water is respired.
(4) ACT AS AMPHOTERIC MOLECULE
• Water molecule acts both as acid and a base. As acid, it gives up electron to form H+ ion, while as a base, it gains electron to form OH ions.
H2O ? H+ + OH-
• It acts as buffer and prevents changes in the pH of living body.
(5) PROTECTION
• Water is an effective lubricant that provides protection against damage resulting from friction.
• It also forms a fluid cushion around organs that helps to protect them from trauma.
(6) AS REAGENT /TURGIDITY
• Water acts as a reagent in many processes such as photosynthesis and hydrolysis reactions.
• It also provides turgidity to the cells.

ORGANIC COMPOUNDS
Those compounds containing carbon (other than carbonates) are called organic compounds. E.g: carbohydrates, Proteins, Lipids and Nucleic acid.

INORGANIC COMPOUNDS
Those compounds, which are without carbon, are called inorganic compounds. E.g: water, carbondioxide, acids , bases and salts.

MACROMOLECULES
Huge and highly organized molecules which form the structure and carry out the activities of cells are called “Macromolecules” Macromolecules can be divided into four major groups.
• Proteins
• Carbohydrates
• Lipids
• Nucleic acids.

MONOMERS
Macromolecules are composed of large number of low molecular weight building blocks or subunits called “Monomers” E.g: Amino-acids (Protein).

CONDENSATION
The process by which two monomers are joined is called “Condensation”.
In this process two monomers join together when a hydroxyl(OH) group is removed from one monomer and a hydrogen (-H) is removed from other monomer.
This type of condensation is called “Dehydration Synthesis” because water is removed (dehydration ) and a bond is made (synthesis).

HYDROLYSIS
A process during which polymers are broken dawn into their subunits (monomers) by the addition of H2O called “Hydrolysis “. It is just reverse of the condensation.

FUNCTIONAL GROUPS
These are particular group of atoms that behave as a unit and give organic molecules their physical, chemical properties and solubility in aqueous solution. E.g
• Methyl group (CH3-)
• Hydroxyl or Alcohol group (OH-)
• Carboxylic acid or Organic-acid group (COOH-)
• Amino or Amine group (NH2-)
• Carbonyl group (CO=)
• Sulfhydryl group (SH-)

PROTEINS
These are the complex organic compounds having C, H,O and N as elements but sometimes they contain P and S also. Due the presence of N they are called “Nitrogenous Compounds” Proteins constitute more than 50% of dry weight of cell. They are present in all types of cells and in all parts of the cell.


CHEMICAL COMPOSITION OF PROTEINS
• Proteins are polymers of amino-acids and number of amino-acids varies from a few to 3000 or even more in different proteins.
• These amino-acids are linked together by specialized bond or linkage called “peptide linkage”
• Each proteins has a unique sequence of amino-acids that gives the unique properties to molecules.

AMINO ACID
It is the basic structural unit of proteins and all amino-acids have an “Amino group (NH2-) and a “Carboxyl group (COOH-)” attached to the same carbon atom, also known as “Alpha carbon”. The have the general formula as:
1. A hydrogen atom.
2. An amino (NH2) group.
3. A carboxyl group (COOH)
4. “Something else” this is the “R” group.
R
¦
H2N -C - COOH
(Amino group) ¦ (Carboxylic group)
H
“R” may be a “H” as in glycine, or CH3 as in alanine, or any other group. So amino acids mainly differ in the R-group.

POLYPEPTIDES
Amino Acids are linked together to from polypeptides of proteins. The amino group of one amino acids may react with the carboxyl group of another releasing a molecule of water. E.g: Glycine and analine may combine to form a dipeptiede

PEPTIDE LINKAGE/ BOND
The linkage between the hydroxyle group of carboxyl group of one amino-acid and the hydrogen of amino-group of another amino-acid release H2O and C-N link to form a bond called “Peptide bond”.


TYPES OF PROTEINS ON THE BASIS OF STRUCTURE
There are four basic structural levels of proteins.

(A) PRIMARY STRUCTURE
• A polypeptide chain having a linear sequence of amino-acids.
• Disulphide (S-S) bond is other important characteristic of the primary protein.
E.g: Insulin Polypeptide chain.

(B) SECONDARY STRUCTURE
• In this type polypeptide chain of amino-acids become spirally coiled.
• This coiling results in the formation of a rigid and tubular structure called “Helix”

(C) TERTIARY STRUCTURE
• Polypeptide chain bends and folds upon it self forming a globular shape.
• It is maintained by three types of bonds. Namely ionic, hydrogen and disulfide (S-S).

(D) QUATERNARY STRUCTURE
• This type is usually present in highly complex proteins in which polypeptide tertiary chains are aggregated and held together by hydrophobic interactions, hydrogen and ionic bonds.
E.g: Haemoglobin molecule.


FUNCTIONS OF PROTEIN
• They Build many Structures of the cell E.G: Plasma Membrane.
• All enzymes are proteins and in this way they control the whole metabolism of the cell.
• Skin, nails, hair, feather, horn etc. contain portion called keratin.
• Casein is the milk portion and ovalbumin is the egg white protein.
• Collagen present in bones, cartilage, etc. is the most abundant protein in higher vertebrates.
• Protein acts as antibodies, antigens and fibrin etc.


CARBOHYDRATES
It is a group of organic compounds having carbon, oxygen and hydrogen, in which hydrogen and oxygen are mostly found in the same ratio as in water i.e. 2:1 and thus called “Hydrated carbons” They are found about 1% by weight and generally called Sugars or saccharides” due to their sweet taste except polysaccharides.


CLASSIFICATION OF CARBOHYDRATES
The carbohydrates can be classified into following groups on the basis of number of monomers.
1. Monosaccharide
2. Oligosaccharides
3. Polysaccharides.

(1) MONOSACCHARIDES
• These are called “Simple Sugars”, because they can not be hydrolysed further into simple sugars.
• Their general formula is “Cn H2n On
• They are white crystalline solids with sweet taste and soluble in water.
• They are present in various fruits and vegetables.
E.g: Glucose, Galactose, Fructose and Ribose etc. Monosaccharide can be sub-classified according to umber of carbon atom present in each molecule. They may be triose, (Glycerose), tetrose (erythrose), pentose, (ribose), hexone (glucose) or heptose (Glucoheptose) having 3,4,5 ,6 and 7 carbon atoms respectively.

(2) OLIGOSACCHARIDES
• These carbohydrates yield 2to 10 monosaccharides mnolecules on hydrolysis
• Disaccharides are the most common and abundant carbohydrates of oligosaccharides.
• These sugars are comparatively less sweet in taste, and less soluble in water.
E.g: Maltose, Sucrose and lactose etc.

(3) POLYSACCHARIDES
• These are the most complex and most abundant carbohydrates in nature.
• They are of high molecular weight carbohydrate which on hydrolysis yield mainly monosaccarides or products related to monosaccharide.
• These sugars are formed by the condensation of hundreds of thousands of monosaccharide units.
• They are tasteless and only sparingly souble in H2O.
E.g: Strach, cellulose Glycogen , Dextrin Agar, pectin and Chitin etc.


FUNCTIONS OF CARBOHYDRATES
• Carbohydrates are the potential source of energy.
• They act as storage food molecules and also work as an excellent building, protective and supporting structure.
• They also form complex conjugated molecules.
• They are needed to synthesize lubricants and are also needed to prepare the nectar in some flowers.


LIPIDS
These are naturally occurring compounds, which are insoluble in water but soluble in organic solvents. They contain carbon, hydrogen and oxygen like carbohydrates rate but in much lesser ratio of oxygen than carbohydrates. These biomolecules are widely distributed among plants and animals.


CLASSIFICATION OF LIPIDS
Following are the important groups of lipids.
1. Acylglycerol (fats and oil)
2. Waxes
3. Phospholipids.
4. Terpenoids.

(1) ACYLGLYCEROL (FATS AND OIL)
• These are found in animals and plants, provide energy for different metabolic activates and are very rich in chemical energy.
• They are composed of glycerol and fatty acids. The most widely spread acylglycerol is triacyl glycerol, also called triglycerides or natural lipids.
• There are two types of acylgycerol

(A) SATURATED ACYLGLYCEROL
• They contain no double bond.
• They melt at higher temperature than unsatured acylglycerols.
• Lipids containing saturated acylgycerol are solid and known as Saturated lipids.
E.g: Butter and Animal fat. etc.

(B) UNSATURATED ACYLGLYCEROL
• They contain unsaturated fatty acids i.e they contain one or more than one double bond between carbon atom(C=C-).
• They are liquid at ordinary temperature .
• They are found in plant also called “Oil”
E.g: linolin found in cotton seeds etc.

(2) WAXES
Chemically waxes are mixtures of long chain alkanes and alcohols. Ketones and esters of long chain fathy acids
• Waxes are widespread as protective coatings of fruits and leaves some insects also secrete wax.
• Waxes protect plants form water loss and abrasive damage.
• They also provide water barrier for insects, birds and animals etc.

(3) PHOSPHOLIPIDS
• It is most important class of lipids from biological point of view and is similar to riacylglycerol or an oil except that one fatty acid is replaced by phosphate group.
• The molecule of phospholipids consist of two ends, which are called hydrophilic (water loving end (head) and hydrophobic (water fearing)end (Tail).
• These are frequently associated with membranes and are related to vital functions such as regulation of cell permeability and transport process.

(4) TERPENOIDS
• It is large and important class of lipids containing “Isoprenoid “ unit (C5H8).
• They help in oxidation reduction process, act as components of essential oils of plants and also found in cell membrances as “cholesterol

SUB-CLASSES OF LIPIDS
1. Terpenes
2. Steroids.
3. Carotenoids.

(1) TERPENES
• This group based only on “Isoprenoid” unit and they are usually volatile in nature produce special fragrance.
• Derivatives of this group are found in vitamin A and are also important constituents of chlorophyll and cholesterol biosynthesis.
• They are utilized in synthesis of “Rubber” and “Latex”, and some of these are used in perfumes.

(2) STEROIDS
This group of Terpenoids contains 17 carbon atoms ring called “steroid nucleus”.

(3) CAROTENOIDS
They consist of fatty acid like carbon chain and usually found in plants, for example carotene, xanthophylls etc.

NUCLEIC ACIDS
Nucleic Acids Were First Isolated In 1870 By an Austrian Physician Fridrich Micscher from the nuclei of pus cells. These bio molecules are acidic in nature and present in the nucleus.

TYPES OF NUCLEIC ACIDS
Nucleic acids are of two types.
1. Deoxyribonucleic acid or DNA
2. Ribonucleic acid or RNA

CHEMICAL NATURE OF NUCLEIC ACID
Nucleic acids are complex substances. They are polymers of units called nucleotides. DNA is made up of deoxyribonucleotides, while RNA is composed of ribo nucleotides.

STRUCTURE OF NUCLEOTIDE
Each nucleotide is made of three subunits
(a) 5-carbon monosaccharide (a pentose sugar)
(b) Nitrogen containing base.
(c) Phosphoric acid.

(A) PENTOSE SUGAR
Pentose sugar in RNA is ribose, while in DNA it is deoxyribose.

(B) NITROGENOUS BASE
Nitrogenous bases are of two types
(i) PYRIMIDINES (SINGLE RINGED): These are cytosine (abbreviated as C), thymine (abbreviated as T), and uracil (abbreviated as U).

(ii) PURINES (DOUBLE RINGED): These are adenine (abbreviated as A) and guanine(abbreviated as G).

C) PHOSPHORIC ACID
Phosphoric acid (H3PO4) has the ability to develop ester linkage with OH group of pentose sugar.

FORMATION OF NUCLEOTIDE
Formation of nucleotide takes place in two steps. First the mitrogenous base combines with pentose sugar at its first carbon to form a “Nucleoside”. In second step the phosphoric acid combines with the 5th carbon of pentose sugar to form a “Nucleotide”.


(A) MONONUCLEOTIDES
• They exist singly in the cell or as a part of other molecules.
• These are not the part of DNA or RNA and some of these have extra phosphate groups e.g ATP.

(B) DINCULEOTIDES
These nucleotides are covalently bounded together and usually act as co-enzymes
E.g NAD (Nicotinamide dinucleotide ).

(C) POLYNUCLEOTIDES
• Nucleotides are found in the nucleic acid as “Polynucleotide” and they have a variety of role in living organisms.
• They usually perform the function of transmitters of genetic information.
CONJUGATED MOLECULES
• Two different molecules, belonging to different categories, usually combine together to form “Conjugated molecules”.
• These conjugated molecules are not only of structural, but also are of functional significance.
• They play an important role in regulation of gene expression.

(A) GLYCOPROTEIN AND GLYCOLIPIDS
Carbolydrates may combine with proteins to form glycoprotein or with lipids to form glycolipid.

FUNCTIONS
(a) Most of cellular secretions are glycoprotein’s in nature.
(b) Both glycoproteins and glycolipids are integral structural components of plasma membranes.

(B) LIPOPROTEINS
Combination of lipids and proteins form lipoproteins.
FUNCTION
They are basic structural framework of all types of membranes in the cells.

(C) NUCLEOPROTEINS
Nucleic acids have special affinity for basic proteins . they are combined together to form nucleoproteins.
FUNCTIONS
The nucleoproteins (Histone) are present in chromosomes.

THINGS TO BE REMEMBER
• Proteins-Berzelius and G.J murlder.
• Lipids-Bloor in 1943.
• DNA –Hereditary material.
• RNA- carrier of genetic information.
• rRNA – (Ribosomal RNA)- Double stranded.
• Transcription- Formation of mRNA.
• Translation –Formation of Proteins by ribosmes.