Fluid along with all the structures of cell bounded within the limits of cell membrane, is known as protoplasm. So protoplasm includes plasma membrane, cytoplasm and nucleus. Protoplasm of a single cell is called Protoplast (wall less cell)

1. BIOMOLECULES
* Fluid along with all the structures of cell bounded within the limits of cell membrane, is known as protoplasm. So
protoplasm includes plasma membrane, cytoplasm and nucleus. Protoplasm of a single cell is called Proto-
plast (wall less cell).
* Word protoplasm has Originated from a greek word (Protos = first, Plasma = organisation).
* Protoplasm was first observed by Corti, 1772.
* Felix Dujardin, 1835 observed jelly like substance in animal cells (protozoa) and gave the name 'Sarcode'.
* J.E. Purkinje, 1840 observed similar substance in plant cells and coined the term 'Protoplasm'.
* Max Schultze, 1861 established similarity between sarcode and protoplasm. Schultze proposed protoplasm
theory (name given by O. Hertwig). Max Schultze firstly told that protoplasm is physical basis of life.
* J.S. Huxley, 1868 wrote a book "Protoplasm is physical basis of life"
PHYSICAL NATURE OF PROTOPLASM
Colloidal Theory - "Fisher 1894, Hardy" 1899 and "Wilson" 1925.
This is most acceptable theory for protoplasm. According to this theory, the protoplasm is a Polyphasic
Colloidal System.
PHYSICAL PROPERTIES OF PROTOPLASM
(1) Protoplasm is a translucent, odourless and polyphasic fluid.
(2) Protoplasm is a crystallo-colloid type of solution.
Protoplasm is a mixture of such chemical substances among which some form crystalloid i.e. true solution
(Sugars, Salts, Acids, Bases etc.) and others which form colloidal solution (Proteins, Lipids etc.)
(3) Size of colloidal particles (0.001 to 0.1 m.) is between true solution and suspension.
(4) Colloidal systems composed of two stages. (i) Dispersion phase or continuous form or intermicelleus and
(ii) Dispersed phase or discontinuous phase or Micellus
On the basis of dispersion and dispersed phases there are four types of colloids-
(A) Sol = Dispersion phase is liquid and dispersed phase is solid. In sol stage, protoplasm is less viscous.
Protoplasm in sol stage occurs in majority of living cells.
(B) Gel = Dispersion phase is solid and dispersed phase is liquid. Protoplasm is more viscous e.g. Skin Cells.
(C) Emulsion - Both stages are liquid i.e. fluid colloidal particles are dispersed in a liquid matrix e.g. blood
plasma composed of both sol and emulsion.
(D) Aerosol - solid particles remain suspended in gas e.g. smoke. Aerosol does not occur in living system.
(5) Protoplasm mainly composed of either sol or gel.
(6) Sol stage provides cyclosis, Brownian movements and high reactivity to protoplasm.
(7) Gelation of protoplasm provides elasticity, contractibility, rigidity and viscosity.
(8) Colloid particles have electric charge and due to charges these remain in a continuous random motion, called
Brownian movement.
(9) Environmental conditions like temperature, pressure and pH cause changes in the properties of protoplasm.
This change brings endocellular movement of protoplasm called cyclosis.
(10) Brownian movement and cyclosis are more significant in sol stage of protoplasm.
(11) Being a liquid mixture, the protoplasm has a surface tension. Solutes (Proteins and lipids) having less surface
tension, form a delimiting membrane at surface. This membrane is called Interface membrane (Plasma mem-
brane).
Interface membrane has power of rapid regeneration.

2. (12) Being colloid, protoplasm exhibits "Tyndal effect" i.e. Scattering of incident light rays.
(13) Sol and gel stages of protoplasm are interconvertible so the protoplasm is a reversible colloidal system. Non
living colloids are irreversible.
(14) Ageing - With age, charges of colloid particles diminishes, brownian movements stops so ultimately it becomes
non reactive (death of protoplasm).
(15) Viscosity of protoplasm = 2–20 centipoises
(16) pH = 6-8
(17) Refractive index = 1.4
BIOLOGICAL PROPERTIES OF PROTOPLASM
Protoplasm is a living substance so it posseses biological properties also.
(1) Protoplasm has motion due to cyclosis, amoeboid and Brownian movement. These movements depend on age
of cells, amount of water, genetic factors and chemical composition of protoplasm.
(2) Protoplasm exhibits irritability when provided stimuli.
Sensitivity of protoplasm to external stimuli is called irritability. Transmission of stimuli from one place to an-
other is called conductivity.
Besides irritability, conductivity also occurs in protoplasm of many cells e.g. nerve cells, muscle cells etc.
(3) Different chemical reactions takes place in protoplasm. Constructive reactions are called Anabolic processes
like synthesis of different types of biomolecules. Destructive reaction like oxidation of food is called catabolic
processes. Anabolic and Catabolic Processes collectively called metabolism.
(4) Protoplasm has the capacity to take external material and resynthesize them in a new form (assimilation).
(5) Respiration and excretion.
CHEMICAL NATURE OF PROTOPLASM
Approximately 34 elements participate in the composition of protoplasm but only 13 elements are main or universal
elements in protoplasm i.e. C, H, O, N, Cl, Ca, P, Na, K, S, Mg, I, Fe.
Carbon, Hydrogen, Oxygen and Nitrogen form the 96% part of protoplasm.
S. No. Elements % Amount
1. Oxygen 62
2. Carbon 20
3. Hydrogen 10
4. Nitrogen 3
5. Calcium 2.5
6. Phosphorus 1.14
7. Chlorine 0.16
8. Sulphur 0.14
9. Potassium 0.11
10. Sodium 0.10
11. Magnesium 0.07
12. Iodine 0.014
13. Iron 0.010

3. Rest of the elements of protoplasm occur in very small quantity (0.756%). These are, therefore called Trace
elements. These includes Copper, Cobalt, Manganese, Zinc, Boron, Vanadium, Chromium, Tin, Silicon, Fluo-
rine, Molybdenum, Nickel, Selenium, Arsenic.
COMPOUNDS OF PROTOPLASM
Although some elements occur in protoplasm as free ions but mostly two or more elements are variously
combined to form different kinds of compounds.
Inorganic compounds :
1. Water = 70–90%
2. Salts, acids, bases, gases = 1– 3%
Organic Compounds :
1. Proteins = 7–14%
2. Lipids = 1–3%
3. Carbohydrates = 1–2%
4. Nucleic acids, enzymes and other = 1-3%
Biomolecule All the carbon compound that Present in living tissue.
Biomolecule
Micromolecule
(Mol. W
eight <1000 daltons)
Macromolecule
(Mol.W
eight > 1000 daltons)
Present inacid soluble pool Present in acid insoluble pool
Amino acids, N base, Monosaccharides, Lipid
2
eg
Protein, nucleic acid, Polysaccharide
eg
Lipids is exceptionary micromolecule but present in acid insoluble pool.
WATER :
(1) It is a best solvent in nature, it forms the fluid matrix of protoplasm. All other constituents of protoplasm are its
solutes.
(2) Being an ideal dispersion medium, it causes Brownian movement of colloid particles, resulting into their collision
and mutual bombardment. This facilitates reactivity between the various compounds necessory for maintaining
protoplasm in live state.
(3) It causes streaming or cyclosis in protoplasm transportation of solutes from one part to the others.
(4) It itself participates in certain types of chemical reactions, particularly in the hydrolytic breakdown of complex
compounds.
(5) Having a high specific heat, it minimises temperature variations and thus protects protoplasm against ill effects
of sudden rise or fall of temperature in the environment.
(6) Of total water, 95% water is free water and 5% water occurs as bound water.
(7) Water in human body - 65-70% of total body weight.
(8) Human body 40 litre :
55% (22 litre) – intracellular fluid
45% (18 litre) – extracellular fluid

4. (9) In animal kingdom - Hardest material : Enamel
(10) In plant kingdom - Hardest material : Sporopollenin
SALTS :
(1) Salts in protoplasm occur in ionised form. These ions are responsible for electric conductivity, rendering proto-
plasm irritable and response to environmental changes.
(2) These provides linkage or chemical bonds in many chemical reactions. Such type of linkage called "Salt link-
age".
(3) Some metallic and other ions such as Mg, Fe, Zn, Mo, Mn etc. act as cofactors in enzymatic activities.
(4) These regulate the osmotic pressure and chemical exchange of protoplasm from its environment.
(5) Some ions also act as co-factor :
Zn+2
– Carbonic anhydrase Fe+2
– Aconitase, catalase
Cu+2
– Tyrosinase [CBSE 2004] Mo – Nitrogenase
Mg+2
– Co-factor of many respiratory enzymes like Kinase, Enolase, Dehydrogenase
Ni – Urease enzyme
(6) Some other functions of ions :
Na+
, K+
ions – Nerve induction
Ca+2
, Mg+2
ions – Muscle contraction, Reduce more excitability of nerves and muscle.
Ca+2
ion – Blood clotting, Bone formation
– Most abundant mineral element in animal body
Na+
, K+
ions – Main component of ringer solution.
K+
ion – Helpful in seismonastic movement, stomatal opening and closing.
ACIDS AND BASES :
These prevent pH variations by forming a buffer system in protoplasm, for e.g. carbonic acid-Bicarbonate
buffer system.
ORGANIC COMPOUNDS OF PROTOPLASM :
CARBOHYDRATES
 Main source of energy.
 First respiratory substrate – carbohydrate
 R.Q. = 1 R Q
CO
O
. .






2
2
 Compounds of Carbon, Hydrogen and Oxygen with ratio of H and O is 2:1, so they are also called as hydrates
of carbon.
 Generalised formula of carbohydrates is Cx
(H2
O) y.
 Simple carbohydrates which are soluble in water and sweet in taste are called "Sugar".
 Carbohydrates are main source of energy in body. In a normal man 55-65% of energy is available to him is in
the form of carbohydrates present in his diet.

5. CLASSIFICATION OF CARBOHYDRATES :
On the basis of numbers of saccharides in hydrolysis, Carbohydrates are classified as Monosaccharides, Oligo
saccharides and Polysaccharides.
A. Monosaccharides :–
1. They are simplest sugars which can not be further hydrolysed.
2. In their generalised formula x is always equal to y i.e. number of Carbon and Oxygen atoms same.
3. First step of oxidation – Phosphorylation
4. All monosaccharides occur in d and l form, except the Dihydroxy acetone.
CH2
OH
|
C = O
|
CH2
OH
Dihydroxy acetone
5. The structure of saccharides is either ring or straight chain.
6. A six membered ring is known as pyranose and five membered ring is furanose.
Pyranose and furanose names were given by "Haworth."
7. Anomer – In aqueous solution, Glucose occurs in cyclic structure. In anomers, position of –H and –OH
groups are changed on C1
carbon atom.
H– C=O
1
H– C– OH
2
HO– C– H
3
H– C– OH
4
H– C– OH
5
H– C– OH
6
H
Glucose (Straight chain)
CHOH
2
C
H
O
OH
C
H
H
C
OH
C
C
H
H
OH
OH
-Glucose (Pyranose structure)
CHOH
2
C
H
O
OH
C
H
H
C
OH
C
C
H
H OH
OH
-Glucose
H
H– C – OH
C=O
HO– C– H
H– C – OH
H
Fructose (Straight chain)
H– C – OH
H– C – OH
Epimer : Isomer formed as a result of interchange of the –OH and –H groups on carbon atom 2, 3 and 4 of
glucose, are known as epimer.

6. Epimer of Glucose :
Mannose (Difference on C2
carbon)
Galactose (Difference on C4
carbon)
1
C
H– C– OH
2
HO– C– H
3
HO– C– H
4
H– C
5
6
CHOH
2
Galactose
H OH
O
1
C
H– C– OH
2
HO– C– H
3
H– C– OH
4
H– C
5
6
CHOH
2
Glucose
H OH
O
1
C
HO– C– H
2
HO– C– H
3
H– C– OH
4
H– C
5
6
CHOH
2
Mannose
H OH
O
On the basis of number of carbon atoms monosaccharides are classified in following groups.
(i) Trioses – C3
H6
O3
e.g. Glyceraldehyde and Dihydroxy acetone. PGAL and DHAP are precursors
of all other carbohydrates.
(ii) Tetroses – C4
H8
O4
e.g. Erythrose, Erythrulose
(iii) Pentoses – C5
H10
O5
e.g. Ribose, Ribulose, Xylulose, Arabinose,*Deoxyribose (C5
H10
O4
)
(iv) Hexoses – C6
H12
O6
e.g. Glucose, Fructose, Galactose, Mannose, *Rhamnose (C6
H12
O5
)
(v) Heptose – C7
H14
O7
e.g. Sedoheptulose
* Chemically all carbohydrates are polyhydroxy aldehyde or ketones.
* Monosaccharides with free aldehyde group are termed as Aldoses (PGAL, Erythrose, Ribose, Arabinose,
Deoxyribose, Glucose, Galactose, Mannose).
* While monosaccharides with free ketone group are called ketoses (DHAP, Erythrulose, Ribulose, Xylulose,
Fructose, Sedoheptulose).
All monosaccharides are "reducing sugars" as their free aldehyde or ketone groups are capable of reducing
Cu++
to Cu+
.
This property is the basis of Benedict's test or fehling's test used to detect the presence of glucose in urine.
* Beside RNA, ribose sugar is an important component of ATP, NAD, NADP and FAD
* In deoxyribose the second carbon is devoid of oxygen atom
* Arabinose occurs in "Gum arabic" .
* Glucose is dextrorotatory so it is called "dextrose"
* Glucose is found in grapes in abundant quantity so it is also known as "grape sugar"
* Glucose is the main respiratory substrate in the body. Other types of hexose are converted into glucose by liver.
* Fructose is Laevorotatory so it is called "Laevulose".
* Fructose is found in honey and sweet fruits so it is called as "Fruit Sugar".
* Fructose is the sweetest sugar.
* Galactose is not found in free stage.
* In mammalian body, galactose occurs as a part of milk sugar lactose.

7. * Galactose is also found as a component of glycolipids (for e.g. cerebrosides) and pectin, Hemi cellulose etc.
* Mannose not found in free state.
* Mannose occurs in albumin of egg and in wood as component of hemicellulose.
* Glucose is also known as blood sugar.
* Aspartame is most commonly used artificial sweetner.
* Most sweetest chemical substance is Thaumatine, Obtained from a bacteria Thaumatococcus danielli .
* Galactose is known as brain-sugar
DERIVATIVES OF MONOSACCHARIDES
(1) Amino sugars – Formed by the displacement of hydroxyl group from second carbon atom by amino group
e.g. Glucosamine, Galactosamine.
(2) Sugar alcohol – Aldehyde group (-CHO) of the sugar is changed to primary alcohol (-CH2
OH). Sorbitol and
Mannitol are respectively formed from glucose and mannose.
(3) Sugar acids – They are formed by the oxidation of terminal -CHO or -CH2
OH group of sugar to produce
carboxyl group -COOH e.g. Glucoronic acid, Galacturonic acid.
B. Oligo – Saccharides
Oligo – Saccharides are those carbohydrates which on hydrolysis yield 2 to 10 monosaccharide units (mono-
mers). In oligosaccharides, monosaccharides are linked together by glycosidic bonds. Aldehyde or ketone group
of one monosaccharide reacts with alcoholic group of another monosaccharide to form glycosidic bond. One
molecule of H2
O eliminates during glycosidic bond formation (dehydration synthesis). Direction of glycosidic
bond is 1'-4".
When another monosaccharide unit is fructose then the direction of linkage is 1'-2". (Non reducing sugars). For
e.g. Sucrose
Types of Oligosaccharides :–
(i) Disaccharides – composed of two monosaccharide units. e.g. Maltose, Sucrose, Lactose, Trehalose.
* All disaccharides are water soluble and sweet in taste, so they are known as sugar.
* Maltose is commonly called malt sugar. It is intermediate compound in starch digestion. Maltose has 1'-4"
glycosidic linkage between -D glucose and -D glucose
* Lactose is milk sugar with  -1'-4" glycosidic linkage between glucose and galactose
* Lactose is least sweetest sugar.
* Maximum % of lactose = Human milk 7%
* In plants transport of sugar is present in form of sucrose.
Glucose Glucose
Maltose

8. * Sucrose is also known as invert sugar.
* Sucrose is called Cane Sugar or Table Sugar or Commercial Sugar. Sucrose composed of  -D Glucose and
fructose.
* Trehalose is present in haemolymph of insects. It has glycosidic linkage between two anomeric carbon ( -
glucose and  -Glucose).
(ii) Trisaccharides – e.g. Raffinose (Galactose+Glucose+Fructose)
(iii) Tetrasaccharides – e.g. Stachyose (Gal. + Gal. + Glu. + Fructose)
(iv) Pentasaccharides – e.g. Barbascose (Gal. + Gal. + Glu. + Glu + Fructose)
Raffinose and stachyose occur in phloem and may be employed for translocation of
carbohydrates.
C. Polysaccharides :–
* Poly saccharides composed of large number of monosaccharide units.
* Suffix '---an' is added in their names and they are known as glycans.
* Pentose polysaccharides are called pentosans for e.g.
araban (from L- arabinose), xylan (from D-xylose), all these found in cell wall.
* Hexose polysaccharides are called "hexans". for e.g. mannan (from mannose) cellulose, starch etc.
* Polysaccharides are insoluble in water and do not taste sweet.
* All polysaccharide are non-reducing
* Although polysaccharide is non reducing but in a polysaccharide chain one end is reducing and another end
is non reducing.
* According to function, they are classified as nutritive and structural.
On structural basis polysaccharides are of two types.
(I) Homopolysaccharides :–
Composed of same monomers. Biologically important homopolysaccharides are as follows:
(a) Cellulose :– Linear polymer of  -D-glucose units (6000 to 10,000). It has  1'-4" linkage. Partial
digestion yields a cellobiose units (Disaccharide).
Cellulose is main component of plant cell wall. In wood, cellulose is 50% and in cotton, it is 90%.
* Most abundant organic molecule on earth.
* In urochordates animals their occur cellulose like material and it is called "Tunicine" It is also called
Animal cellulose.
* It is also used to form Rayon fibre (Artificial silk).
* Paper made from plant pulp is cellulose.
(b) Starch – It is main stored food in plants. Starch is polymer of  -D-glucose units. Starch consits of two
types of chains.
(i) Amylose :– 250-300 glucose units are arranged in an unbranched chain by  1'-4" linkage.
(ii) Amylopectin :– A branched chain molecule. Approximately 30 glucose units are linked by  -
1',4" and  - 1', 6" linkage.
. Amylose gives blue colour with iodine.

9. . Amylopectin gives red colour with iodine.
. Starch present in potato contains 20% amylose and 80% amylopectin.
. Starch form helical structure so starch can hold I2
molecules in the helical portion so starch-I2
is blue in
colour. While cululose have linear structure so it cannot hold I2
and don’t give Iodine test.
(c) Glycogen :– Storage form of carbohydrate in animals, storage region of glycogen is liver and muscles.
Storage of glycogen liver > muscle. Glycogen is also called as animal starch. Glycogen is highly branched
polymer of  -D-glucose.
. Glycogen is formed by the 1',4" bond linkage at long chain and 1',6" bond linkage at branching point.
. Glycogen gives red colour with iodine.
. Glycogen is store food of fungi.
(d) Chitin :– Linear polymer of N-acetyl- D-glucosamine with –1', 4"–linkage.
. N-acetyl D-glucosamine is an amino acyl (-NH-CO-CH3
)derivative of -D-glucose.
. Chitin is an important component of exoskeleton of Arthropods and cell walls of fungi.
. Second most abundant organic molecule on earth.
. It is also called Fungal cellulose.
(e) Inulin :– Linear polymer of fructose units linked with  -1',2" bonds. Inulin is found in roots of Dahalia
and Artichoke. It is water soluble polysaccharide and it is used to know the glomerular filteration rate.
. It is smallest storage polysaccharide.
(f) Dextrin – Dextrin is an intermediate substance in the digestion of glycogen and starch. By hydrolysis of
dextrin, glucose and maltose are formed. It also occurs as stored food in yeast and bacteria.
(II) Heteropolysaccharide :–
Composed of different monosaccharide units.
(a) Hyaluronic acid – Found in vitreous humour, umbilical cord, joints and connective tissue in the form of
lubricating agent. It also occurs in animal cell coat as binding material (Animal cement).
. Hyaluronic acid is made up of D-glucuronic acid and N-acetyl – D-glucosamine arranged in alternate
orders. These different monosaccharides have –1',3" bonds and such disaccharides have –1', 4" bonds.
(b) Chondriotin – D-glucuronic acid + N-acetyl galactosamine.
. Chondriotin occurs in connective tissue.
. Sulphate ester of chondriotin is main structural component of cartilages, tendons and bones.
(c) Heparin – It is anticoagulant of blood. Heparin is made up of D-glucuronic acid and N-sulphate glu-
cosamine arranged in alternate order
(d) Pectins – Methylated galacturonic acid + galactose + arabinose.
. Pectin found in cell wall where it binds cellulose fibrils in bundles.
. Salts of pectin i.e. Ca and Mg-pectates form middle lamella in plants.
. It is also called Plant cement.
(e) Hemicellulose – Mannose + Galactose + Arabinose + Xylulose.
. Store material – Phytalophus (Ivory palm). Hemicellulose which is obtained from this plant is white, hard
and shiny and it is used to form billiard ball and artificial ivory.

10. MUCOPOLYSACCHARIDES
Slimy polysaccharides with capacity to bind proteins and water are called mucopolysaccharides. In plants,
mucilage is a common mucopolysaccharide formed of galactose and mannose units.
Hyaluronic acid, chondriotin, heparin are other examples.
Special Points :
1. Peptidoglycan – Present in cell wall of bacteria.
– Composed of N - acetyl Glucosamine + N - acetyl muramic acid + peptide chain
of 4-5 amino acids
2. Agar-Agar – It is a mucopolysaccharide which is obtained from some red algae – Gracilaria,
Gelidium, Chondrus. It is composed of D-galactose and L-galactose unit and after
every 10th
unit a sulphate group is present it is used for preparing culture medium (1,
3 linkage)
3. Difference between gums and fevicol  Gums are natural mucoplysaccharide while fevicol is
synthetic rubber based adhesive.
LIPIDS
* Fat and its derivatives are combinaly known as lipid.
* Lipid term coined by Bloor.
* Compounds of C, H, O but the ratio of Hydrogen and Oxygen is not 2:1. The amount of oxygen is considerably
very less.
* Lipids are insoluble in water and soluble in organic solvents like acetones, chloroform, benzene, hot alcohol,
ether etc.
* Lipids occur in protoplasm as minute globules.
* Lipids do not form polymer.
* Lipids provide more than double energy as compare to carbohydrate.
* In animals, fat present in subcutaneous layer and working as food reservoir and shock-absorber.
* Lipid requires less space for storage as compare to carbohydrate because lipid molecule is hydrophobic and
condense.
* Animals store maximum amount of food in the form of lipid.
* Lipid provides maximum amount of metabolic water as compare to carbohydrate and protein on oxidation.
* Lipids are not strictly macromolecules.
* Lipids are called fats and oils on the basis of melting point. Oils have lower melting point and fats have higher
melting point.
* Some lipid also have phosphorus like lecithin.
(A) Simple Lipid or Neutral Fats :–
* These are esters of long chain fatty acids and alcohol. In majority of simple lipids, the alcohol is a trihydroxy
sugar alcohol i.e. glycerol.
* Three molecules of fatty acid linked with one molecule of glycerol. The linkage is called "ester bond". such type
of lipids called Triglycerides. Three molecules of water are released during formation of triglycerides (dehydra-
tion synthesis)
* Glycerol is also known as trihydroxy propane.
* Similar or different fatty acids participate in the composition of a fat molecule. Simple lipids contain two types
of fatty acids.

11. (i) Saturated Fatty acids :- are those in which all the carbon atoms of hydro-carbon chain are saturated
with hydrogen atoms
e.g. Palmitic acid (16-carbon comound)
Stearic acid
(ii) Unsaturated fatty acids :– acids are those in which some carbon atom are not fully occupied by
hydrogen atoms
e.g. Oleic acid
Linoleic acid
Linolenic acid
Arachidonic acid (20-carbon comound)
Polyunsaturated = fatty acids with more than one double bonds in their structure e.g. Linoleic acid, Linolenic
acid, Arachidonic acid, Prostagladins (derived from arachidonic acid)
. Unsaturated fatty acid also called as essential fatty acids because no animal is able to synthesize them.
. Simple lipids with saturated fatty acid remain solid at normal room temperature e.g. fats
. Simple lipids with unsaturated fatty acids remain liquid at room temperature e.g. oils.
. Saturated fatty acids are less reactive so they tend to store in body and cause obesity.
. Unsaturated fatty acids are more reactive so they tend to metabolise in body and provide energy.
. Oils with poly unsaturates are recommended by physicians for persons who suffer from high blood choles-
terol or cardio-vascular diseases. This is because increasing the proportion of poly unsaturated fatty acids
to saturated fatty acids, without raising the fats in the diet tend to lower the cholesterol level in blood.
Waxes :– are monoglycerides with only one molecule of fatty acid attached to a long chain monohydroxy
alcohol. Waxes are more resistant to hydrolysis as compared to triglycerides. Waxes have an important role in
protection. They form water insoluble coatings on hair and skin in animals and stem, leaves and fruits of plants.
e.g.
Bees Wax (Hexacosyl palmitate)
Carnauba (Myricyl cerotate) which occurs on leaves, stem and fruits.
Spermaceti In skull of whale and Dolphin.
Cerumen or ear wax - occurs in external auditory meatus
Lanoline or cholesterol ester– occurs in blood, sebum and gonadial ducts as lubricating agent.
It is also obtained from wool of sheep.
(B) Conjugated or Compound Lipids :–
(1) Phospholipids or phosphatide or phospholipins :–
2 Molecules of fatty acid + Glycerol + H3
PO4
+ Nitrogenous compound. Phospholipids are most abun-
dant type of lipids in protoplasm.
Phospholipids have both hydrophilic polar end (H3
PO4
and nitrogenous compound) and hydrophobic non
polar end ( fatty acids). Such molecules are called amphipathic. Due to this property, phospholipids form
bimolecular layer in cell membrane.
Some biologically important phospholipids are as following :
(a) Lecithin or Phosphatidyl choline
* Nitrogenous compound in lecithin is choline
* Lecithin occurs in egg yolk, oil seeds and blood.
* In blood lecithin functions as carrier molecule. It helps in transportation of other lipid.

12. (b) Cephalin–Similar to lecithin but the nitrogenous compound is ethanolamine, cephalin occurs in
nervous tissue, egg yolk and blood platelets.
(c) Sphingolipids or sphingomyelins similar to lecithin but in place of glycerol it contains an amino
alcohol sphingosine.
Sphingolipids occur in myelin - sheath of nerves, other examples of phospholipid are phosphati-
dyl serine, phosphatidyl inositol, plasmologens.
(2) Glycolipid :– 2 fatty acid + sphingosine + galactose
eg. Cerebroiside which occurs in white matter of brain -
Gangliosides - These occur in nerve ganglia and spleen. These also contain N-acetyl neurominic
acid and glucose beside other compounds.
(3) Derived Lipids :– Lipid derived from simple or conjugated lipid .Derived lipids are complex in struc-
ture. They are insoluble in water and soluble in organic solvents
(1) Steroids :– Steroids exhibit tetracyclic structure called
"Cyclo pentano perhydrophenanthrene nucleus"
On the basis of functional group, steroids are of two types -
(a) Sterols :– Alcoholic steroids e.g. cholesterol – Cholesterol abundantly occurs in brain, nervous
tissue , Adrenal gland and skin. Cholesterol is a parent steroid. Several other biologically important
steroids are derived from cholesterol.7 - dehydro cholesterol which occurs in skin is a provitamin.
On exposure to ultraviolet radiation, it transforms in cholecalciferol i. e vitamin D
* Cholesterol is also called "most decorated micromolecule in biology".
Ergosterol :– It occurs in oil seed , fungi like ergot and yeast . Ergosterol is precursor of another
form of Vitamin D–Ergocalciferol.
Coprosterol :– Occurs in faecal matter. It forms by decomposition of cholesterol by colon bacteria
Bile acid :– Bile Juice contains different types of steroid acids. e. g. cholic acid, Lithocholic acid etc.
They help in emulsification of fats.
(b) Sterones :– Ketonic steroids, for e. g. sex hormones, Adreno corticoids , ecdyson hormone of
insects,Diosgenin obtained from yam plant (Dioscorea), is used in manufacture of antifertility pills.
(2) Chromolipid = It is also called terpene.
* Most complex lipid in protoplasm.
* Chromolipids composed of repeated isoprene units
Example : Carotenoids, vitamin A, E, K, Natural Rubber (Polyterpene).
CH =C– CH=CH
2 2
CH3
(Isoprene)
PROTEINS
Protein name is derived from a greek word which means " holding first place" (Berzelius and Mulder)
* Essential elements in protein are C , H , O, N,
* Most of the proteins contain sulphur. In some proteins iodine , iron and phosphorus are present.

13. * After water, proteins are most abundant compounds in protoplasm. (7-14%) amount of proteins.
* Proteins are polymer of amino acid (Fisher and Hofmeister). There are approximately 300 amino acids known
to exist but only 20 types of amino acids are used in formation of proteins
* Proteins are hetero Polymer of amino acid.
* Amino acids contain an amino group and carboxylic group on the same carbon i.e. the -carbon so they are
called -amino acid.
* Amino acid are substituted methane.
NH —C—COOH
2
H
H
Glycine
NH —C—COOH
2
CH3
H
Alanine
NH —C—COOH
2
CH – OH
2
H
Serine
* Each amino acid is amphoteric compound because it contains one acidic -COOH and a alkaline group -NH2
* In protoplasm free amino acid occurs as ions ( at iso electric point )
R
H
NH3
+
C COOH   

  
   

  

R
H
NH2 C COO
Zwitter ion
* Iso electric point is that point of pH at which amino acids do not move in electric field.
* Out of 20 amino acids, 10 amino acids are not synthesized in body of animals so they are must in diet. These
are called Essential amino acid . e. g. Threonine , Valine, Leucine, Isoleucine, Lysine, Methionine, Phe-
nylalanine Tryptophan, Arginine, Histidine. Arginine and Histidine are semi essential.
* 10 amino acids are synthesized in animal body so these are called Non essential amino acids. for e.g.
Glycine, Alanine, Serine, Cysteine,Aspartic acid, Glutamic acid, Asparagine, Glutamine, Tyrosine, Proline
Classification of Amino Acids :–
(A) Amino acids can be classified on the basis of their R group –
(1) Non-polar R group - Glycine, Alanine, Valine, Leucine, Isoleucine, Proline, Methionine, Phenyl alanine,
Tryptophan.
(2) Polar but uncharged R group - Serine, Threonine, Cysteine, Tyrosine, Asparagine, Glutamine
(3) Positively charged polar R-group - Lysine, Arginine, Histidine (Basic Amino acid)
(4) Negatively charged polar R-group - Aspartic acid, Glutamic acid (Acidic Amino acid)
Except glycine, each amino acid has two enantiomeric isomers
D–amino acid L–amino acid
* Eucaryotic proteins have L- amino acid while D- amino acid occurs in bacteria and antibodies:
Amino acids are joined with peptide bond to form protein.

14. H
C
R
C
HN
2
H
C
R
C
N OH+ HO
2
O O
H
Peptide bond
Dipeptide
* Peptidyl transferase enzyme catalyses the synthesis of peptide bond.
* Property of protein depends (i) on sequence of amino acid and (ii) configuration of protein molecules.
Special Points on Amino acid :
* Glycine is the simplest and Tryptophan is complex Amino acid.
* Cysteine, Cystine, Methionine are the sulphur containing Amino acid.
* Phenyl alanine, Tyrosine, Tryptophan amino acids are aromatic Amino acid.
* Serine & Threonine are alcoholic amino acid.
* Histidine, Proline & hydroxyproline are heterocyclic amino acid.
* All the amino acids are laevo-rotatory, except Glycine which is non-rotatory.
* Amino acids which participate in protein synthesis called protein Amino acid and which do not participate
called non-protein.
eg. GABA, Ornithine, Citrulline.
* Proline, Hydroxy proline contain imino group 







|
NH instead of amino group so they are also called imino acid.
Configuration of Protein Molecule :–
(1) Primary configuration or structure :– A straight chain of amino acids linked by peptide bonds form
primary structure of proteins. This structure of proteins is most unstable. Newly formed proteins on ribosomes
have primary structure.
(2) Secondary configuration :– Protein molecules of sec. structure are spirally coiled. In addition to peptide
bond, amino acids are linked by hydrogen bonds form between oxygen of one amide group and hydrogen
of another amide group. This structure is of two types -
i –Helix :– Right handed rotation of spirally coiled chain with approximately 3
1
2
amino acids in each
turn. This structure has intramolecular hydrogen bonding i. e. between two amino acids of same chain
e.g. Keratin ,Myosin, Tropomyosin.
(ii)  Helix or pleated sheath structure :- Protein molecule has zig zag structure. Two or more
protein molecules are held together by intermolecular hydrogen bonding. e.g. Fibroin (silk).
. Proteins of sec. structure are insoluble in water and fibrous in appearance.
. Keratin is a fibrous , tough, resistant to digestion, sclero protein.Hard ness of keratin is due to abundance
of cysteine amino acid in its structure.
(3) Tertiary Structure :– Proteins of tertiary structure are highly folded to give a globular appearance. They
are soluble in water (colloid solution). This structure of protein has following bonds–
(i) Peptide bonds = strongest bond in proteins.

15. (ii) Hydrogen bonds
(iii) Disulphide bond :– These bonds are formed between - SH group of amino acid (Cysteine). These
bonds are second strongest bond and stabilise tertiary structure of protein.
(iv) Hydrophobic bond : Between amino acids which have hydrophobic side chains for e.g. Aromatic
amino acid
(v) Ionic bond : Formation of ionic bond occurs between two opposite ends of protein molecule due to
electrostatic attraction
Majority of proteins and enzymes in protoplasm exhibit tertiary structure.
(4) Quaternary Structure :– Two or more poly peptide chains of tertiary structure unite by different types
of bond to form quaternary structure of protein. Different polypeptide chains may be similar (lactic-dehy-
drogenase) or disimilar types (Haemoglobin, insulin).
Quaternary structure is most stable structure of protein.
Significance of Structure of Protein :–
* The most important constituents of animals are protein and their derivatives. Proteins form approximately
15%ofanimalprotoplasm. The physicalandbiologicalproperties ofproteinsaredependant upontheir secondary
and tertiary configurations. Protein is electrically charged because it has NH3
+
and COO ionic components.
In an acidic medium the COO group of protein converts to COOH and the protein itself becomes
positively charged. In contrast, in an alkaline medium the NH3
+
group of protein changes to – NH2
+ H2
O and
as a result it becomes negatively charged. Therefore, at a specific pH a protein will possess an equal number
of both negative and positive charges and it is at this specific pH a protein becomes soluble.
* If the pH changes towards either acidic or alkaline side, then the protein begins to precipitate. This property
of protein has great biological significance. The cytoplasm of cells of organisms has an approximate pH of
7 but the pH of proteins present in it is about 6 and thus, the proteins are present in a relatively alkaline
medium. Therefore, the proteins are negatively charged and also are not in a fully dissolved state. It is because
of this insolubility, proteins form the structural skeleton of organismal cells. Similarly, the pH of nucleoplasm
is about 7 but the pH of proteins, namely, histones and protamines, in it is relatively more. Therefore, as
a resultthey arepositively chargedand donot remainfully dissolvedinthenucleoplasm forming minute organelles,
the most important being the chromosomes.
* As has been described above, the structural units namely amino acids of proteins contain both a carboxyl
group ( COOH) or acidic group and an amino group ( NH2
) or alkaline group attached to the same carbon
atom. Therefore, proteins depending upon the pH of the medium can exhibit both alkaline and acidic properties.
Such compounds which exhibit both acidic and alkaline properties are called amphoteric compounds or zwitter
ions. In the protoplasm, this dual property of proteins is utilized for neutralization of strong acids and alkalis
since the protein acts as an ideal buffer in either of the situations.
* Besides changes in pH, salts, heavy metals, temperature, pressure, etc. also cause precipitation of proteins.
Because of these changes, the secondary and tertiary configuration of proteins is destroyed and many times
the tertiary structured gobular proteins become converted to secondary configuration fibrous proteins. Such
alternations in the physical state of proteins is called denaturation. If the change in the medium of protein
is mild and for a short period, then denaturation of the protein is also temporary, however, if the change
in medium is strong and prolonged then denaturation is permanent and the protein becomes coagulated.
For example, the white or albumen of egg is a soluble globular protein but on heating it permanently coagulates
into fibrous insoluble form. It is clear, that strong alternations result in the denaturation of proteins and they
lose their biological properties and significance. It is this reason, that cells of organisms are unable to bear
strong changes and they ultimately die.

16. Types of protein
Simple
(made upof only amino acids)
Compound Derived
Fibrous
Long, Coiled &Thread like
Globular
Collagen :-
– Most abundant protein in animal body
– 1/3 part of total proteins
– Present in connective tissue
– Threads of collagen known as T
endon
Elastin :-
– In connective tissue
– Threads of Elastin known as Ligament
Keratin
Rubisco :-
– Present in chloroplast.
– M
ost abundant protein on the earth.
Albumin :-
– M
aintain B.C.O.P
.
– In milk as Lactoalbumin
– In egg yolk as Ovalbumin
– In blood as Serumalbumin
Globin :- Present in Haemoglobin.
Protamine :- Present in the nucleus of Sperm
H
istone protein :- Present with eukaryotic DNA.
– In it Lysine &Arginine A.A. are present in
more amount.
Prolamine :- Present as store protein in cereal grains.
In Barley as Hordein
In M
aize as Zein
In W
eat as Gladein, Gluten, Glutelline.
* Elasticity in wheat flour is due to Glutelline.
Compound protein
Non-protein part
Made up of A.A.
non amino acid part
(Prosthetic group)
Protein part
* Types of compound protein on the basis of prosthetic group.
1. Nucleoprotein :- Prosthetic group is nucleic acid.
eg. Chromosome = DNA + RNA + Protein
Ribosome = rRNA + Protein
Virus
2. Chromoprotein :- Prosthetic group is Porphyrin pigment (metal + porphyrin ring)
eg. Metal Colour
Haemoglobin Fe Red
Cytochrome Fe Red
Chlorophyll Mg Green
Haemocyanin Cu Blue

17. 3. Lipoprotein :- Prosthetic group is lipid
eg. Plasma membrane
Lipovitelline membrane on egg surface.
4. Phosphoprotein :- Prosthetic group is phosphoric acid (H3
PO4
)
 Caseinogen - Milk
 Pepsin - Protein digesting emzyme.



Phosvitin
Egg
Ovovitelline
5. Lecithoprotein :- Prosthetic group is Lecithin
eg. Fibrinogen - Blood
6. Metalloprotein :- Prosthetic group is metal
eg. Enzyme with its co-factor
7. Glycoprotein :- Prosthetic group is carbohydrate (less than 4% carbohydrate)
eg. (1) Mucin - Saliva
(2) Erythropoetin - Kidney.
(3) A & B antigen of RBC.
(4) globulin of blood.
(5) FSH - Follicular stimulating hormone
(6) LH - Leutinizing hormone
Glycoproteins which are present on cell surface are helpful in cell recognition.
Human = Egg surface - Fertilizin - Glycoprotein
Sperm surface - Antifertilizin - Simple protein.
8. Mucoprotein Prosthetic group is carbohydrate (more than 4% carbohydrate)
e.g. Mucoids of synovial fluid, Osteomucoprotein of bones,
Tendomucoprotein of tendons, Chondromucoprotein of cartilage.
* Derived protein
Primary Secondary
Formed by denaturation Formed by digestion
eg. Fibrinogen
Myosin
Fibrin -
Myosan -
eg. Protein - Proteoses - Peptone - Polypeptide - Peptide - A.A.
Special Points on Protein :
* Monomeric protein : Protein composed of one polypeptide chain.
* Oligomeric/Polymeric/Multimeric protein : Protein composed of more then one polypeptide chains.

18. NUCLEIC ACIDS
* F. Meischer discovered nucleic acid in nucleus of pus cell and called it "nuclein". The term nucleic acid was
coined by "Altman."
* Nucleic acids are polymer of nucleotides.
= Nitrogen base + pentose sugar + phosphate
On the basis of structure nitrogen bases are broadly of two types :–
1. Pyrimidines – Consist of one pyrimidine ring. Skeleton of ring composed of two nitrogen and four Carbon
atoms. e.g. Cytosine, Thymine and Uracil.
CYTOSINE URACIL THYMINE
2. Purines - Consist of two rings i.e. one pyrimidine ring (2N + 4C) and one imidazole ring (2N + 3C) e.g.
Adenine and Guanine.
ADENINE GUANINE
Pentose Sugar :–
Ribose Deoxy ribose Phosphate
Nitrogen base forms bond with first carbon of pentose sugar to form a nucleoside. Nitrogen of third place
(N3
) forms bond with sugar in case of pyrimidines while in purines nitrogen of ninth place (N9
) forms bond
with sugar.
Phosphate forms ester bond (covalent bond) with fifth Carbon of sugar to form a complete nucleotide.
O
CH2
H
H
OH
3'
H
H
2'
N
H
N
7
8
9
6
5 1
2
4
N H
N
H
H
3
P
O
O
O
4'
5'
O
1'
H
N
Deoxyribose
Phosphate
Nucleoside
Nucleotide

19. Types of Nucleosides and Nucleotides
1. Adenine + Ribose = Adenosine
Adenosine + Phosphate = Adenylic acid (AMP)
2. Adenine + Deoxyribose = Deoxy adenosine
Deoxy adenosine + P = Deoxy adenylic acid (dAMP)
3. Guanine + Ribose = Guanosine
Guanosine + P = Guanylic acid (GMP)
4. Guanine + Deoxyribose = Deoxy guanosine
Deoxy guanosine + P = Deoxy guanylic acid (dGMP)
5. Cytosine + Ribose = Cytidine
Cytidine + P = Cytidylic acid (CMP)
6. Cytosine + Deoxyribose = Deoxycytidine
Deoxycytidine + P = Deoxycytidylic acid (dCMP)
7. Uracil + Ribose = Uridine
Uridine + P = Uridylic acid (UMP)
8. Thymine + Deoxyribose = Deoxy thymidine
Deoxythymidine + P = Deoxythymidylic acid (dTMP)
DNA
* Discovered by - Meischer
* DNA term was given by - Zacharis
* In DNA pentose sugar is deoxyribose sugar and four types of nitrogen bases A,T,G,C
* Wilkins and Franklin studied DNA molecule with the help of X-Ray crystallography.

20. * With the help of this study, Watson and Crick (1953) proposed a double helix molel for DNA. For this
model Watson, Crick and Wilkins were awarded by Noble Prize in 1962.
* One main hallmark (main point) of double helix model is complementary base pairing between purine and
purimidine.
* According to this model, DNA is composed of two polynucleotide chains.
* Both polynucleotide chains are complementary and antiparallel to each other.
* In both strand of DNA direction of phosphodiester bond is opposite. i.e. If direction of phosphodiester bond
in one strand is 3'-5' then it is 5'-3' in another strand.
* Both strand of DNA held together by hydrogen bonds. These hydrogen bonds are present between nitrogen
bases of both strand.
* Adenine binds to thymine by two hydrogen bonds and cytosine binds to guanine by three hydrogen bonds.
* In a DNA molecule one purine always pairs with a pyrimidine. This generates approximately uniform distance
between the two strands of DNA.
* In DNA plane of one base pair stacks over the other in double helix. This, in addition to H-bonds, confers stability
of the helical structure of DNA.
* Chargaff's equivalency rule - In a double stranded DNA amount of purine nucleotides is equals to amount
of pyrimidine nucleotides.
Purine= Pyrimidine
[A] + [G] = [T] + [C]
   
   
A G
T C


 1
* Base ratio =
A T
G C


= constant for a given species. i.e. species specific.
* In a DNA A + T > G + C A – T type DNA. Base ratio of A – T type of DNA is more than one.
eg. Eukaryotic DNA
* In a DNA G + C > A + T G – C type DNA. Base ratio of G – C type of DNA is less than one.
eg. Prokaryotic DNA
* Melting point of DNA depends on G – C contents.
More G – C contents means more melting point.
Tm
= Temperature of melting.
Tm
of prokaryotic DNA > Tm
of Eukaryotic DNA
* DNA absorbs U.V. rays means 2600Å wavelength.
* Out of two strand of DNA only one strand participates in transcription, it is called Antisense strand/ Non
coding strand/Template strand.
* Other strand of DNA which does not participate in transcription is called Sense strand/Coding strand .
* Denaturation and renaturation of DNA - If a normal DNA molecule is placed at high temperature (80-
90°C) then both strands of DNA will separate from each other due to breaking of hydrogen bonds. It is called
DNA-denaturation.
When denatured DNA molecule is placed at normal temperature then both strand of DNA attached and
recoiled to each other. It is called renaturation of DNA.
* Hyperchromicity - When a double stranded DNA is denatured by heating then denatured DNA molecule
absorbs more amount of light, this phenomenon is called hyperchromicity.

21. * Hypochromicity - When denatured DNA molecule cool slowly then it becomes double stranded and it absorb
less amount of light. This phenomenon is called hypochromicity.
Configuration of DNA Molecule :–
* Two strands of DNA are helically coiled like a revolving ladder. Back bone of this ladder (Reiling) is composed
of phosphates and sugars while steps (bars) are composed of pairs of nitrogen bases.
* Distance between two successive steps is 3.4 A0
. In one complete turn of DNA molecule there are such 10 steps
(10 pairs of nitrogen bases). So the length of one complete turn is 34 A0
. This is called helix length.
* Diameter of DNA molecule i.e. distance between phosphates of two strands is 20A0
.
* Distance between sugar of two strands is 11.1 A0
.
* Length of hydrogen bonds between nitrogen bases is 2.8-3.0 A0
. Angle between nitrogen base and C1
Carbon
of pentose is 510
.
* Each step of ascent is represented by a pair of bases. At each step of ascent, the strands turns 36°.
* Molecular weight of DNA is 106
to 109
dalton.
* Innucleusofeukaryotes the DNAisassociatedwithhistone proteintoform nucleoprotein. Histone occupiesmajor
groove of DNA at 300
angle.
* Bond between DNA and Histone is salt linkage (Mg+2
).
* DNA in chromosomes is linear while in prokaryotes, mitochondria and chloroplast it is circular.
* In  x 174 bacteriophage the DNA is single stranded and circular isolated by Sinsheimer.
G–4, S–13, M–13, F1
and Fd – Bacteriophages also contain ss–circular DNA.
Types of DNA :–
On the basis of direction of twisting, there are two types of DNA.
1. Right Handed DNA -
Clockwise twisting e.g. The DNA for which Watson and Crick proposed model was 'B' DNA.
DNA Helix Length No. of Distance between Diameter
base pairs two pairs
'A' 28 A0
11 pairs 2.56 A0
23 A0
'B' 34 A0
10 pairs 3.4 A0
20 A0
'C' 31 A0
9.33 pairs 3.32 A0
19 A0
'D' 24.24 A0
8 pairs 3.03 A0
19 A0
2. Left handed DNA :–
Anticlockwise twisting e.g. Z-DNA - discovered by Rich. Phosphate and sugar backbone is zig-
zag. Units of Z-DNA are dinucleotides (purine and pyrimidine in alternate order)
Helix length – 45.6 A0
Diameter – 18.4 A0
No. of base pairs – 12 (6 dimers)
Distance between 2 base - pairs – 3.75 A0

22. * Palindromic DNA – Wilson and Thomas
 

C C G G T A C C G G
G G C C A T G G C C
 

Sequence of nucleotides same from both ends.
Special Points :
* DNA molecule is Dextrorotatory while RNA molecule is Laevorotatory.
* C – value = Total amount of DNA in a haploid genome of organism.
* Oswald Avery, Colin Macleod and Maclyn Mccarty firstly proved the genetic material is DNA.
* Alfred Hershey and Martha Chase Firstly proved that in bacteriophage DNA is also genetic material.
* A molecule that can act as a genetic material must fulfil the following criteria–
(i) It should be able to generate it’s replica (replication)
(ii) It should chemically and structurally be stable
(iii) It should has property of mutation.
(iv) It should be able to express itself in the form of “Mendelian Characters”.
D.N.A. REPLICATION
* D.N.A. is the only molecule capable of self duplication so it is termed as a " Living molecule"
* All living beings have the capacity to reproduce because of this characteristic of D.N.A.
* D.N.A replication takes place in "S - Phase" of the cell cycle. At the time of cell division, it divides in equal
parts in the daughter cells.
SEMI CONSERVATIVE MODE OF D.N.A. REPLICATION
Semi conservative mode of D.N.A. replication was first proposed by Watson & Crick. Later on it was
experimentally proved by Meselson & Stahl (1958) on E - Coli and Taylor on Vicia faba (1958).To
prove this method, Taylor used Radiotracer Technique in which Radioisotopes (tritiated thymidine = 1
H
3
) were
used. Meselson and Stahl used heavy isotope (N15
) and Cairns (1963) used radioactive thymidine.

23. * Due to the replication of active Thymidine containing D.N.A., two D.N.A. molecules were obtained in which
50% radioactivity was found.
* When these two D.N.A. molecules containing active Thymidine were made to replicate, the next time four
D.N.A. molecules were obtained. Out of these 4 D.N.A. , 2 D.N.A. molecules were radioactive and remaining
2 were not radioactive.
* In the same sequence, the obtained D.N.A. molecules were further made to replicate then also the no : of
radioactive D.N.A. remains 2.
MECHANISM OF D.N.A. REPLICATION
The following steps are included in D.N.A. replication :-
(1) Unzipping (Unwinding) :–
* The separation of 2 chains of D.N.A. is termed as unzipping. And it takes place due to the breaking of
H–bonds. The process of unzipping starts at a certain specific point which is termed as initiation point or
origin of replication . In prokaryotes there occurs only one origin of replication but in eukaryotes there
occur many origin of replication i.e. unzipping starts at many points simultaneously. At the place of origin,
the topoisomerase enzyme (a type of endonuclease) induces a cut in one strand of DNA (Nicking) to relax
the two strands of DNA.
* The enzyme responsible for unzipping (breaking the hydrogen bonds) is Helicase (= Swivelase). In the process of
unzipping Mg+2
act as cofactor. Unzipping takes place in alkaline medium.
* A protein, "Helix destabilizing protein" prevents recoiling of two separated strands during the process of replication.
An another protein SSB (single stranded DNA binding protein) prevents the formation of bends or loops in
separated strands.
DNA–Gyrase – A type of topoisomerase prevents supercoiling of DNA.
Note :–
The process of D.N.A. replication takes a few minutes in prokaryotes and a few hours in Eukaryotes.
(2) Formation of New Chain :–
* To start the synthesis of new chain, special type of R.N.A. is required which is termed as R.N.A. Primer.
The formation of R.N.A. primer is catalysed by an enzyme - R.N.A. Polymerase (primase). Synthesis of
RNA–primer takes place in 5' 3' direction. After the formation of new chain, this R.N.A. is removed.
For the formation of new chain Nucleotides are obtained from Nuceloplasm. In the nucleoplasm, Nucleotides
are present in the form of triphosphates like dATP, dGTP, dCTP, dTTP etc.
* During replication, the 2 phosphate groups of all Nucleotides are separated. In this process energy is yeilded
which is consumed in D.N.A. replication. So, it is clear that D.N.A. does not depend on mitochondria for it's
energy requirements.
* Energetically replication is a very expensive process.. Daoxyribonucleoside triphosphase serve duas purposes
in addition to acting as substrates they provide energy for polymerisation.
* The formation of new chain always takes place in 5' - 3' direction. As a result of this, one chain of D.N.A.
is continuously formed and it is termed as Leading strand. The formation of second chain begins from the
centre and not from the terminal points, so this chain is discontinuous and is made up of small segments
called Okazaki Fragments . This discontinuous chain is termed as Lagging strand. Ultimately all these
segments joined together and a complete new chain is formed.

24. * The Okazaki segments are joined together by an enzyme DNA Ligase.(Khorana)
* The formation of new chains is catalysed by an enzyme DNA Polymerase. In prokaryotes it is of 3 types:
(1) DNA - Polymerase I :- This was discovered by KORNBERG (1957). So it is also called as 'Kornberg's
enzyme'. Kornberg also synthesized DNA first of all, in the laboratory. This enzyme functions as exonuclease.
It separates RNA - primer from DNA and also fills the gap.It is also known as DNA-repair enzyme.
(2) DNA - Polymerase II :- It is least reactive in replication process. It is also helpful in DNA-repairing
in absence of DNA-polymerase-I and DNA polymerase-III
(3) DNA - Polymerase III :- This is the main enzyme in DNA - Replication. It is most important. It was
discovered by Delucia and Cairns. The larger chains are formed by this enzyme. This is also known
as Replicase . DNA – polymerase III is a complex enzyme composed of seven polypeptides
i.e. , ,, , 1
, , 2
.
In Eucaryotes, there occur five types of DNA–polymerase enzyme.
(1) –DNA – polymerase = It is concern with lagging strand synthesis.
(2) –DNA – polymerase = It concerned with DNA repair.
(3) –DNA – polymerase = It concerned with replication of cytoplasmic DNA.
(4) –DNA – polymerase = It is concern with leading strand synthesis.
(5) – DNA polymerase = It is concern with proof reading.
* Thus DNA - Replication process is completed with the effect of different enzymes.
* In the semi conservative mode of replication each daughter DNA molecule receives one chain of polynucleotides
from the mother DNA - molecule and the second chain is synthesized.
Special Point :
 All DNA polymerase I, II and III enzymes have 5'-3" polymerisation activity and 3'-5" exonuclease activity.
 Any failure in cell division after DNA replication result into polyploidy.
 Difference between DNAs and DNase is that DNAs menas many DNA and DNase means DNA digestive enzymes.
RIBO NUCLEIC ACID (RNA)
Structure of RNA is fundamentally same as DNA, but there are some differences. The differences are as follows:-
(1) In place of De-oxyribose sugar in DNA, there is present Ribose sugar in RNA.
(2) In place of nitrogen base Thymine in DNA, there is present uracil in RNA.
 The presence of thymine at the place of uracil also provide additional stability to DNA.
(3) RNA is made up of only one polynucleotide chain i.e. R.N.A. is single stranded .
Exception :–
RNA found in Reo - virus is double stranded, i.e. it has two polynucleotide chains.
*  × 174 bacteriophage has 5386 nucleotides. -bacteriophage has 48502 base pairs, Escherichia coli has
4.6 × 106
base pairs and 6.6 × 109
base pairs in human (2n).
* 2-OH groups present at every nucleotide in RNA as reactive group and makes RNA labile and easily degradable
and RNA also has catalytic function so it is more reactive so DNA is chemically less reactive and structurally
more stable as compared to RNA.

25. * DNA is more stable so preferred for storage of genetic information but for the transmission of genetic information
RNA is better.
* RNA being a catalyst was reactive and hence unstable. Therefore DNA has evolved from RNA with chemical
modification that make it more stable. DNA being double stranded and having complementary strand further
resists changes by evolving a process of repair.
Types of RNA :
1. Genetic RNA or Genomic RNA - In the absence of DNA, sometime RNA works as genetic material and
it transfers informations from one generation to next generation.
eg. Reo virus, TMV, QB bacteriophage.
2. Non-genetic RNA - 3 types -
(A) r - RNA (B) t - RNA (3) m - RNA
RNA functions as adapter, structural and in same cases as a catalytic (Ribozyme)
(1) Ribosomal RNA (r - RNA) :-
* This RNA is 80% of the cell's total RNA
* r RNA was discovered by Kuntze.
* It is found in ribosomes and it is produced in nucleolus.
* It is the most stable form of RNA .
* There are present 80s type of ribosomes in Eukaryotic cells. Their subunits are
60s and 40s. In 60s sub unit of ribosome three types of r–RNA are found – 5s, 5.8s, 28s
* 40s sub unit of ribosome has only one type of r–RNA i.e. 18s.
* So 80s ribosome has total 4 types of r–RNA.
* Prokaryotic cells have 70s type of ribosomes and its subunits are 50s and 30s.
* 50s sub unit of ribosome contains 2 types of r–RNA i.e. 5s and 23s
* 30s sub unit of ribosome has 16s type of r–RNA.
* So 70s RNA has total 3 types of r–RNA.
Function :–
* At the time of protein synthesis, r–RNA provides attachement site to t–RNA and m–RNA and attaches them
on the ribosome.
* The bonds formed between them are known as Salt linkages. It attaches t–RNA to the larger subunit of
ribosome and m–RNA to smaller subunit of ribosome.
(2) Transfer – RNA (t–RNA) :–
* It is 10-15% of total RNA.
* It is synthesized in the nucleus by DNA.
* It is also known as soluble RNA (sRNA)
* It is also known as Adapter RNA.

26. It is the smallest RNA (4s).
Function :– At the time of protein synthesis it acts as a carrier of amino-acids.
Discovery :– t–RNA was discovered by Hogland, Zemecknike and Stephenson.
Structure :– The structure of t - RNA is most complicated.
A scientist named Holley presented Clover leaf model of its structure. In two dimensional structure the
t–RNA appears clover leaf like but in three dimensional structure (by Kim) it appears L–shaped.
The structure of tRNA is looks like a clover leaf but in actual structure, the tRNA is a compact molecule
which looks like inverted 'L'.
* The molecule of t - RNA is of single stranded.
* There are present three nucleotides in a particular sequence at 3' end of t - RNA and that sequence is CCA.
* All the 5' ends i.e. last ends are having G (guanine).
* 3' end is known as Acceptor end.
* t–RNA accepts amino acids at acceptor points. Amino acid binds to 3' end by its – COOH group.
* The molecule of t - RNA is folded and due to folding some complementary nitrogenous bases come across
with each other and form hydrogen bonds.
* There are some places where hydrogen bonds are not formed, these places are known as loop.
C
C
A
5' G
3'
Acceptor arm
T  c Loop
Extra arm
Anticodon/Nodoc
Recognition Loop
DHU Loop
(8-12 bases) (7 bases)
(7 bases)

27. Loops :–
There are some abnormal nitrogenous bases in the loops, that is why hydrogen bonds are not formed.
e.g. (i) Inosine (I) (ii) Pseudouracil () (iii) Dihydrouridine (DHU)
(A) T  C Loop or Attachment loop :–
This loop connects t - RNA to the larger subunit of ribosome.
(B) Recognition Loop (Anticodon loop) :-
* This is the most specific loop of t-RNA and different types of t-RNA are different due to this loop. There
is a specific sequence of three nucleotides called Anticodon, is present at the end of this loop.
* On the basis of Anticodon, there are total 61 types of t-RNA or we can also say that there are 61 types
of Anticodon.
* t–RNA recognizes its place on m - RNA with the help of Anticodon.
* The anticodon of t-RNA recognises its complimentary sequence on m–RNA. This complimentary sequence
is known as codon.
(C) DHU Loop :–
* It is also known as Amino - acyl synthetase recognition loop. Amino - acyl synthetase is a specific type
of enzyme. The function of this enzyme is to activate a specific type of amino acid. after activation this enzyme
attaches the aminoacid to the 3' end of t–RNA.
* There are 20 types of enzymes for 20 types of aminoacids.
* The function of DHU loop is to recognize this specific Aminoacyl synthetase enzyme.
(3) Messenger RNA (m –RNA) :–
* The m - RNA is 1 - 5% of the cell's total RNA.
Discovery :- Messenger RNA was discovered by Huxley, Volkin and Astrachan. The name m-RNA was given
by Jacob and Monad.
* The m - RNA is produced by genetic DNA in the nucleus. This process is known as Transcription.
* It is least stable RNA.
* Both DNA and RNA are able to mutate. In fact, RNA being unstable, mutate at faster rate so virus having RNA
genome and having shorter life span mutate and evolve faster.
* RNA was the first genetic material.

28. * Formation of RNA over DNA template is called transcription. Out of two strand of DNA only one strand
participates in transcription and called ‘‘Antisense strand’’.
* If both strands act as a template during transcription they would code for RNA molecule with different sequence
and If they code for proteins the sequence of aminoacid in these protein would be different and another reason
that if the two RNA molecule produced they would be complementary to each other and form a ds RNA which
prevent translation of RNA.
* A gene is defined as the functional unit of inheritance. It is difficult to literally define a gene in terms of
DNA sequence, because the DNA sequence coding for tRNA or rRNA molecule is also define a gene
(But information of protein is present on the DNA segment which code mRNA. So generally it is
reffered for it)
* The segment of DNA involved in transcription is ‘‘Cistron’’.
* RNA polymerase enzyme is involved in transcription. In eukaryotes there are three types of RNA polymerases.
. RNA polymerase–I for 28s rRNA, 18s rRNA, 5.8s rRNA synthesis.
. RNA polymerase–II for m–RNA synthesis.
. RNA polymerase–III for t–RNA, 5s rRNA, SnRNA synthesis.
* In eukaryotes RNA polymerase enzyme is made up of 10–15 polypeptide chains.
* Prokaryotes have only one type of RNA polymerase which synthesizes all types of RNAs.
* RNA polymerase of E. Coli has five polypeptide chains , ', ,  and .
* polypeptide chain is also known as  factor (sigma factor).
* Core enzyne + Sigma factor  RNA Polymerase
(, ', , ) ()
Following steps are present in transcription –
(1) INITIATION :–
* DNA has a ‘‘Promoter site or initiation site’’ where transcription begins and a ‘‘Terminator site’’
where transcription stops.
* Sigma factor () recognises the promoter site of DNA.
* With the help of sigma factor RNA polymerase enzyme attached to a specific site of DNA called ‘‘Promoter
site’’.
* In prokaryotes before the 10 N2
base from ‘‘Starting point’’ a sequence of 6 base pairs (TATAAT) is present
on DNA, which is called ‘‘Pribnow box’’.
* In eukaryotes before the 20 N2
base from ‘‘Starting point’’ a sequence of 7 base pairs (TATAAAA) or
(TATATAT) is present on DNA which is called "TATA box or Hogness box"
* At promoter site RNA polymerase enzyme breaks H–bonds between two DNA strands and separates them.
* One of them strand takes part in transcription. Transcription proceeds in 5' 3' direction.
* Ribonucleotide triphosphate come to lie opposite complementary nitrogen bases of anti sense strand.
* These Ribonucleotides present in the form of triphosphate ATP, GTP, UTP and CTP. When they are used
in transcription, pyrophosphatase hydrolyse two phosphates from each activated nucleotide. This releases energy.
* This energy is used in the process of transcription.

29. (2) ELONGATION :–
* RNA polymerase enzyme establishes phosphodiester bond between adjacent ribonucleotides.
* Sigma factor separates and core enzyme moves along the anti sense strand till it reaches terminator site.
(3) TERMINATION :–
* When RNA polymerase enzyme reaches at terminator site, it separates from DNA templet.
* At terminator site on DNA, N2
bases are present in palindromic sequence.
* In most cases RNA polymerase enzyme can recognise the ‘Terminator site’ and stop the synthesis of RNA
chain, but in prokaryotes, it recognises the terminator site with the help of Rho factor ( factor).
* Rho () factor is a specific protein which helps RNA polymerase enzyme to recognise the terminator site.
move
Terminator site
Terminator site
Core enzyme released
at terminator site
Factor
Promoter site
Coding strand
Template strand
Core enzyme
Dig. : Transcription in prokaryotes

30. Discovered by sharp and Roberts. They awarded by Nobel Prize in 1993. Gene which contains non functional
part along with functional part is known as split gene. Non functional part is called intron and functional
part is called exon. By transcription split gene produces a RNA which contains coding and non coding sequence
and called hn RNA (Hetero genous nuclear RNA). This hn RNA is unstable. Now 7 methyl guanonsine is
added to its 5' end, and a cap like structure is formed. It is called capping and 200 nucleotides of adenylic
acid are added to its 3' end, which is called poly 'A' tail, Now it becomes stable. By the process of RNA
splicing hn–RNA produces functional mm-RNA that is exonic RNA. In RNA splicing non coding parts removed
with the help of ribonuclease enzyme and coding part join together with the help of RNA ligase. Some specific
proteins are also helpful in RNA - splicing called 'Small nuclear ribonucleoprotein' or 'SnRNP' or 'Snurps'.
These SnRNP proteins combine with some other proteins and SnRNA to form spliceosome complex. This
spliceosome complex uses energy of ATP to cut the RNA, releases the non-coding part and joins the coding-
part to produce functional RNA. Non coding part of hn RNA remained inside the nucleus and not translated
in to protein. Only coding part moves from nucleus to cytoplasm and translated into protein.
Mostly Eukaryotic genes are example of split gene, but gene which forms histone and interferon protein
are non split gene. It contains only and only exonic part.
Mostly prokaryotic genes are example of non split gene.
 In euckaryotes after transcription splicing process also occured.
 The split gene represent an ancient (primitive) feature of gene.
 Presence of intron is a primitive character.
 The splicing process represent the dominance of RNA world.
5 
functional part Non functional part Functional part
3 AntisenseStrandof DNA
Exon Intron Exon
T
ranscription
5 3 
Coding part Non coding part Coding part
HnRNA(unstable)
Stabilization
Coding part Non coding part Coding part
[AAA....]
Poly 'A' tail
5' end
7mGcap
by Guanyl transferase
Splicing
Ribonuclease
RNAlygase
Spliceosome
complex
A
TP
m-RNA
5' end
[AAA....]
Poly 'A' tail
Capping
3' end
(by Poly A Polymerase)
T
ailing
7mGcap

31. A
UAU
UAC
UAA
(terminator)
UAG
(terminator)
CAU
CAC
CAA
CAG
AAU
AAC
AAA
AAG
GAU
GAC
GAA
GAG
G
UGU
UGC
UGA
Terminator
UGG
CGU
CGC
CGA
CGG
AGU
AGC
AGA
AGG
GGU
GGC
GGA
GGG
U
C
A
G
C
UCU
UCC
UCA
UCG
CCU
CCC
CCA
CCG
ACU
ACC
ACA
ACG
GCU
GCC
GCA
GCG





Phe





Leu















Leu










U
UUU
UUC
UUA
UUG
CUU
CUC
CUA
CUG
AUU
AUC
AUA
AUG
GUU
GUC
GUA
GUG
Met















Val















Ser















Pro















Thr















Ala





Tyr
Ochre
Amber





His





Gln





Asn





Lys





Asp





Glu





Cys

 Try















Arg





Ser





Arg















Gly
U
C
A
G
U
C
A
G
U
C
A
G
U
C
A
G
Fig : Triplet codons of mRNA for amino acids represented in tabular form.
Ile

32. GENETIC CODE
* Term Given by George Gamow.
* Discovered by Nirenberg, Mathai and Khorana.
* The relationship between the sequence of amino acids in a polypeptide chain and nucleotide sequence of
DNA or m–RNA is called genetic code.
* There occur 20 types of amino acids which participate in protein synthesis. DNA contains information for
the synthesis of any types of polypeptide chain. In the process of transcription, information is transfered from
DNA to m–RNA in the form of complementary N2
–base sequences.
* m–RNA contains code for each amino acid and it is called codon. A codon is the nucleotide sequence on
m–RNA which codes for particular amino acid ; wherease the genetic code is the sequence of nucleotides
on m–RNA molecule, which contains information for the synthesis of polypeptide chain.
Triplet Code :–
* The main problem of genetic code was to determine the exact number of nucleotide in a codon which codes
for one amino acid.
* There are four types of N2
–bases in m–RNA (A, U, G, C) for 20 types of amino acids.
* If genetic code is singlet i.e. codon is the combination of only one nitrogen
base, then only four codons are possible A, C, G and U. These are insufficient
to code for 20 types of amino acids.
. Singlet code = 41
= 4 × 1 = 4 codons
. If genetic code is doublet (i.e. codon is the combination of two nitrogen
bases) then 16 codons are formed.
. Doublet code = 42
= 4 × 4 = 16 codons.
. 16 codons are insufficient for 20 amino acid
* Gamow (1954) pointed out the possibility of three letters code (Triplet code).
* Genetic code is triplet i.e. one codon consists of three nitrogen bases
Triplet code = 43
= 4 × 4 × 4 = 64 codons
* In this case there occurs 64 codons in dictionary of genetic code.
* 64 codons are sufficient to code 20 types of amino acids.
* H.G. Khorana artificially synthesized an mRNA.
* Severo ochoa enzyme (RNA polymerase enzyme) is also helpful in polymerising RNA with defined sequences
in a template independent manner.
Characteristics of Genetic Code :–
(i) Triplet in Nature :–
* A codon is composed of three adjacent nitrogen bases which specifies the one amino acid in polypeptide
chain.
For Ex. :
. In m–RNA if there are total 90 N2
– bases.
A
C
G
U
Codons
Singlet Code : 4 × 1 = 4 codons
Doublet Code : 4 × 4 = 16 codons
AA AC AG AU
CC CA CG CU
GG GA GC GU
UU UA UG UC

33. . Then this m–RNA determines 30 amino acids in polypeptide chain.
. In above example, number of nitrogen bases are 90 so codons 30 and 30 codons decide 30 amino
acids in polypeptide chain.
(ii) Universality :–
The genetic code is applicable universally. The same genetic code is present in all kinds of living organism
including viruses, bacteria, unicellular and multicellular organisms.
(iii) Non – Ambiguous :–
* Genetic code is non ambiguous i.e. one codon specifies only one amino acid and not any other.
* In this case one codon never code two different amino acids. Exception GUG codon which codes both valine
and methionine amino acids.
(iv) Non – Overlapping :–
A nitrogen base is a constituent of only one codon.
(v) Comma less :–
* There is no punctuation (comma) between the adjacent codon i.e. each codon is immediately followed by
the next codon.
* If a nucleotide is deleted or added, the whole genetic code read differently.
* A polypeptide chain having 50 amino acids shall be specialized by a linear sequence of 150 nucleotides.
If a nucleotide is added in the middle of this sequence, the first 25 amino acids of polypeptide will be same
but next 25 amino acids will be different.
(vi) Degeneracy of Genetic code :–
* There are 64 codons for 20 types of amino acids, so most of the amino acids (except two) can be coded
by more than one codon. Single amino acid coded by more than one codon is called ‘‘Degeneracy of genetic
code’’. This incident was discovered by Baurnfield and Nirenberg.
* Only two amino acids Tryptophan and Methionine are specified by single codon.
UGG for Tryptophan
AUG for Methionine.
* All the other amino acids are specified or coded by 2 to 6 codons.
* Leucine, serine and arginine are coded or specified by 6–codons.
Leucine = CUU, CUC, CUA, CUG, UUA & UUG
Serine = UCU, UCC, UCA, UCG, AGU, AGC
Arginine = CGU, CGC, CGA, CGG, AGA, AGG
* Degeneracy of genetic code is related to third position (3' – end of triplet codon) of codon. The third base
is described as ‘‘Wobbly base’’.
Chain Initiation and Chain Termination Codon :–
* Polypeptide chain synthesis is signalled by two initiation codons AUG or GUG.
* AUG codes methionine amino acid in eukaryotes and in prokaryotes AUG codes N–formyl methionine.
* Some times GUG also functions as start codon it codes for valine amino acid normally but when it is present
at starting position it codes for methionine amino acid.
* Out of 64 codons 3–codons are stopping or nonsense or termination codon.
Nonsense codons do not specify any amino acid.
UAA (Ochre)
UAG (Amber)





Non–Sense Codons or Stop codons
UGA (Opal)
* So only 61 codons are sense codons which specify 20 amino acid.

34. WOBBLE HYPOTHESIS
* It was propounded by CRICK.
* Normally an anticodon recognises only one codon, but sometimes an anticodon recognises more than one codon.
This is known as Wobbling. Wobbling normally occurs for third nucleotide of codon.
* For e.g. anticodon AAG can recognise two codons i.e. UUU and UUC, both stands for phenyl alanine.
Types of m–RNA – m–RNA is of 2 types –
(1) Monocistronic - The m - RNA in which genetic signal is present for the formation of only one polypeptide
chain eg. Eukaryotes.
(2) Polycistronic :– The m–RNA, in which genetic signal is present for the formation of more than one polypeptide
chains eg. Prokaryotes.
* Non sense codons are found in middle position in polycistronic m–RNA.
CENTRAL DOGMA
* Central dogma term was given by Crick.
* The formation (production) of m - RNA from DNA and then synthesis of protein from it, is known as Central
Dogma.
* It means, it includes transcription and translation.
* The central dogma scheme of protein synthesis was presented by Jacob and Monad.
* The detailed study of central dogma was done by Nirenberg, Mathai and Khorana .
* Beedle and Tatum studied central dogma in a fungus Neurospora.
Reverse Transcription :–
* The formation of DNA from RNA is known as Reverse - transcription. It was discovered by Temin and
Baltimore in Rous - sarcoma virus. So it is also called Teminism.
* ss–RNA of Rous–Sarcoma virus (Retro virus) produces ds–DNA in host's cell with the help of enzyme reverse
transcriptase (DNA–polymerase). This DNA is called c–DNA (Complimentary DNA). Some times this DNA moves
in host genome. Such mobile DNA is called "Retroposon" (Oncogene).
PROTEIN – SYNTHESIS
(1) Activation of Amino acid :–
* 20 types of amino acids participate in protein synthesis.
* Amino acid reacts with ATP to form ‘‘Amino acyl AMP enzyme complex’’ , which is also known as ‘Activated
Amino acid’.
Amino acid + ATP
Amino acyl
t RNA synthetase



 Amino acyl AMP–enzyme complex + PP
* This reaction is catalyzed by a specific ‘Amino acyl t-RNA synthetase’ enzyme.

35. * There is a separate ‘Amino acyl t–RNA synthetase’ enzyme for each kind of amino acid.
(2) Charging of t–RNA (Loading of t-RNA) :–
* Specific activated amino acid is recognised by its specific t–RNA.
* Now amino acid attaches to the ‘Amino acid attachment site’ of its specific t–RNA and AMP and enzyme
are separated from it.
Amino acyl AMP–enzyme complex + t–RNA Amino acyl t–RNA complex + AMP + enzyme
* Amino acyl t–RNA complex is also called ‘Charged t–RNA’ .
* Now Amino acyl t–RNA moves to the ribosome for protein synthesis.
(3) Translation :– 3 steps –
(A) Initiation of polypeptide chain :–
* In this step 30 ‘s’ and 50 's' sub units of ribosome, GTP, Mg+2
, charged t–RNA, m–RNA and some
initiation factors are required.
* In prokaryotes there are three initiation factors present – IF1, IF2, IF3.
* In Eukaryotes more than 3 initiation factors are present. Ten initiation factors have been identified in
red blood cells –
eIF1, eIF2, eIF3, eIF4A, eIF4B, eIF4C, eIF4D, eIF4F, eIF5, eIF6.
* Initiation factors are specific protein.
* GTP and initiation factors promote the initiation process.
* Both sub units of ribosome are separated with the help of IF3 factor.
* In prokaryotes with the help of ‘‘S D sequence’’ (Shine–Delgarno sequence) m–RNA recognises
the smaller sub unit of ribosome. A sequence of 8 N2
base is present before the 4-12 N2
base of
initiation codon on mRNA, called "SD sequence". In Smaller subunit of ribosome, a complementary
sequence of "SD sequence" is present on 16 'S' rRNA, which is called "Anti Shine-Delgarno sequence"
(ASD sequence)
* With the help of 'SD' and 'ASD sequence' mRNA recognises the smaller sub unit of ribosome.
* While in eukaryotes, smaller sub unit of ribosome is recognised by "7mG cap".
* In eukaryotes, 18 'S' rRNA of smaller sub unit has a complementary sequence of "7mG cap".
30 ‘S’ sub unit + m–RNA 2
IF3
Mg

 30 ‘S’ m–RNA – complex
* This ‘‘30 ‘S’ m–RNA – complex’’ reacts with ‘Formyl methionyl t–RNA – complex’ and ‘‘30
‘S’ m–RNA – formyl methionyl t–RNA – complex’’ is formed. This t–RNA attaches with codon
part of m–RNA. A GTP molecule is required.
30 ‘S’ m–RNA – complex + Formyl methionyl t–RNA – complex
30 ‘S’ m–RNA formyl methionyl t–RNA – complex
* Now larger sub unit of ribosome (50 ‘S’ sub unit) joins this complex. The initiation factor released and
complete 70 ‘S’ ribosome is formed.
* In larger sub unit of ribosome there are three sites for t–RNA –
‘P’ site = Peptidyl site.
‘A’ site = Amino acyl site.
‘E’ site = Exit site

36. * Starting codon of m–RNA is near to ‘P’ site of ribosome, so t–RNA with formyl methionine amino
acid first attaches to ‘P’ site of ribosome and next codon of m–RNA is near to ‘A’ site of ribosome.
So next new t–RNA with new amino acid always attach at ‘A’ site of ribosome but in initiation step
'A' site is empty.
(B) Chain – Elongation :–
* New tRNA with new amino acid is attaches at 'A' site of ribosome.
* The link between amino acid of 'P' site of t-RNA is broken and t-RNA of P-site is discharged so –
COOH of P-site A.A. becomes free.
* Now peptide bond takes place between – COOH group of P site amino acid and – NH2
group of
A-site amino acid.
* Peptidyl transferase enzyme induces the formation of peptide bond. In peptide bond formation, 23
‘S’ r–RNA is also helpful. This r–RNA acts as an enzyme so it is also called ‘‘Ribozyme’’.
* After formation of peptide bond t–RNA of P site released from ribosome via E-site and dipeptide
attaches with A site.
* Now t–RNA of A site is transferred to P site and  A site becomes empty.
* Now ribosome slides over m–RNA strand in 5' 3' direction. Due to sliding of ribosome on m–RNA,
new codon of m–RNA continuously available at A site of ribosome and according to new codon of
m–RNA new amino acid attaches in polypeptide chain.
* Translocase enzyme is helpful in movement of ribosome (translocation). GTP provides energy for
sliding of ribosome.
* In elongation process some protein factors are also helpful, which are known as ‘Elongation factors’.
* In prokaryotes three ‘Elongation factors’ are present – EF–Tu, EF–Ts, EF–G.
* In Eukaryotes two elongation factors are present – eEF1, eEF2.
AA1
A U G
5 3
P A
AA1
A U G
5 3
P A
AA2
Fig. (1) Fig. (2)
E E
transloca-
tion
P
5 3
A
AA2
AA1
peptide bond
5
AUG
3
AA1
AA2
P A
Fig. (3) Fig. (4)
E
AA3
E

37. AA1
AA2
AA3
AA4
AA5
A
UAA
5 3
Fig. (6)
P
E
AA1
AA2 AA3
P A
5
AUG
3
E
Fig. (5)
(C) Chain – Termination :–
* Due to sliding of ribsome over m–RNA when any Nonsense codon (UAA, UAG, UGA) available
at A site of ribosome, then polypeptide chain terminates.
* The linkage between the last t–RNA and the polypeptide chain is broken by three release factor
called RF1, RF2, RF3 with the help of GTP.
* In eukaryotes only one Release Factor is known – eRF1.
* An mRNA also have some additional sequences that are not translated and are referred as untranslated regions
(UTR). The UTRs are present at both 5'end (before start codon) and at 3'end (after stop codon).
* The UTR(untranslated regions) present on mRNA are required. for efficient translation process (by recognising
the smaller subunit of ribosome by mRNA)
SPECIAL POINTS
(1) The chargaff's rule is not valid (true) for RNA. It is valid only for double helical DNA. i.e. for RNA it is A
 U and G  C.
(2) The duplication of DNA was first of all proved in E. coli bacterium.
(3) E. coli Bacterium is mostly used for the study of DNA duplication.
(4) Hargovind singh Khurana first of all recognised the triplet codon for Cysteine and Valine amino acids .
(5) Cytoplasmic DNA is 1 - 5% of total cell DNA.
(6) Three lady scientists named Avery, Mc - Leod and Mc Carty (by their transformation experiments on bacteria)
Proved that DNA is a genetic material.
(7) Hershey and Chase first of all proved that DNA is genetic material in bacteriophages.

38. (8) Frankel and Conret proved, RNA as a genetic material in viruses (g–RNA).
(9) AUC
ACU





These anticodons do not exist.
AUU
(10) The structure formed by the combination of m - RNA and Ribosomes is known as polyribosomes/Polysomes/
Ergosomes
(11) The formation of t - RNA takes place from the heterochromatin part of DNA.
(12) The formation of m - RNA takes place from the Euchromatin part of DNA.
(13) m - RNA is least stable. It is continuously formed and finished.
(14) In cytoplasm, t - RNA is present in the form of soluble colloid.
(15) Nucleases :– Nucleases are the breaking enzymes of nucleic acids. These are of two types :-
(1) Endo–Nucleases :– These break down the nucleic acids from the inside.
(2) Exo–nucleases :– These break down the nucleic acids from the ends(terminal ends).
These separate each nucleotide.
(16) Some Inhibitors of Bacterial Protein Synthesis :
Antibiotic Effect
Tetracycline Inhibits binding of amino-acyl tRNA to ribosome
Streptomycin Inhibits initiation of translation and causes misreading
Chloramphenicol Inhibits peptidyl transferase and so formation of peptide bonds
Erythromycin Inhibits translocation of ribosome along mRNA
Neomycin Inhibits interaction between tRNA and mRNA
Especial Points :
* Mic RNA : It is synthesized sometime on the sense strand of DNA which is complementary of Antisense strand
which is used for mRNA synthesis. Such RNA is used for regulation of gene expression at the level of translation.
* Higher Nucleotide : Nucleotides which contain more than one phosphate i.e. ATP, ADP.
ATP : Discover - Karl Lohmann. It is made up by Adenine, D-Ribose and three phosphate. It is a high energy
compound that release energy when the bond between the phosphate is broken. In ATP two high energy
bonds are present. ATP is also called energy currency of cell.
A
TP
ADP
AMP
Adenosine
Adenine Ribose Three phosphate radicals
NH2
C
N
HC
C
C
N
N
N
CH
O
C C
H H
H
C
OH
C
H
OH
CH2
OH
O– P – O
O
Ester bond
3000
OH
P– O
O
~
7300
High energy bonds
~
7300 cal/mol
OH
P– OH
O

39. * Iodine number : It is the amount of iodine in gram absorbed by 100 gram fat. It is used to determine the
degree of unsaturation of fat.
* Second genetic code : Interaction between specific t-RNA and amino acyl synthetase enzyme is known as
second genetic code.
GLUT-4 (Glucose transport 4) Proteins : It is a transport protein that allows glucose to enter a cell.
* DNA-quenching : Rapid cooling of denatured DNA, fix it in permanently denatured form, it is called DNA
quenching.
* Secondary metabolites :These are the product of metabolic reactions but they do not directly involve in the
growth, reproduction and development of these organism. Many secondary metabolites are used in human-welfare.
eg. drugs, rubber, spices etc.
NCERT BASED PROBLEMS
1. What are macromolecules? Give examples.
Ans. Macromolecules are large sized, high molecular weight, complex molecules, which are formed by polymerisation
or condensation of small sized, low molecular weight, simple molecules.
e.g. Protein, Nucleic acid and Polysaccharides.
2. Protein having primary structure. If you are given a method to know, which amino acid is at either of the
two termini (ends) of a protein. Can you connect this information to purity or homogeney of a protein?
Ans. No, because we know about the first and last amino acids, but in between them any type of amino acids
may present, for those we can not be sure.
3. Find out and make a list of proteins, used as therapeutic agents.
Ans. Proteins those are engineered in the laboratory for pharmaceutical uses are known as therapeutic proteins.
e.g. Monoclonal antibodies, Interferons, Insulin, Erythropoetin.
4. Can you describe, what happens ? when milk is converted into curd or yoghurt, from your understanding
of proteins ?
Ans. Denaturation (Coagulation) of proteins, present in milk, due to change in pH and temperature.
5. Can you attempt models of biomolecules, using commercially, available atomic models (ball and stick models).
Ans. In ball and stick model, ball is used for atoms and short rod of wood / plastic is used to represent bonds
of a compound.
6. What are gums made of ? Is fevicol different ?
Ans. Gums are colloidal exudates of plant, which are chemically polysaccharide, while fevicol is synthetic rubber
based adhesive.
7. Find out a qualitative test for protein, fat, oils and amino acid.
Ans. Protein  Biuret test
 Alkaline CuSO4 - reagent test
 Violet colour test

40. Fat and Oils
Grease spot test  A drop of oil placed over a piece of simple paper, a translucent spot is visible. This
indicates the presence of fat.
Amino acids  There are different tests available for different amino acids.
Ex :
Test Reagents Colour Amino acid
Millon's test HgNO3 in HNO2 Red Tyrosine and Tryptophan
Xanthoproteic test Conc. HNO3 Yellow Tyrosine, Tryptophan,
Phenylalanine
8. Which property of DNA double helix led, Watson and Crick to give hypothesis for semi-conservative mode
of DNA-replication ? Explain.
Ans. Complementary base pairing between two strands of DNA. They suggested that the two strands would separate
and act as a template for the synthesis of new complementary strand at the time of replication.
9. How did Hershey and Chase differentiate, between DNA and protein in their experiment, while proving, that
DNA is the genetic material?
Ans. They used radioactive phosphorus (P32) in DNA and radioactive sulphur (S35) in protein, Phosphorus present
only in DNA and sulphur present only in protein. So, on the basis of radioactivity in progeny they suggested
that DNA is the genetic material.
10. Differentiate between the following :
(a) mRNA and DNA
(b) Template strand and Coding strand
Ans. (a) mRNA DNA
(1) It contains uracil nitrogen base (1) It contains thymine nitrogen base and
and ribose sugar. de-oxyribose sugar.
(2) It transfers information from (2) It stores genetic information.
DNA in form of protein.
(b) Template strand Coding strand
(1) This strand participates in m-RNA (1) This strand does not participate in mRNA
synthesis. synthesis.
(2) It has 3' – 5" polarity. (2) It has 5' – 3" polarity.
(3) It contains genetic informations. (3) It does not contain genetic informations.
11. Briefly describe the bioinformatics.
Ans. Bioinformatics is the collecting, storage and analysis of large amount of biological data in computer, to make
useful conclusions. These data contain mapping and phenotype informations, nucleotide and amino acids
sequence and structure and function of proteins.