Biological molecules

-> Introduction to Biochemistry

Biochemistry is a branch of science which deals with the chemical
basis of life.
• A! organisms are made up of ce!s
• Ce!s themselves are made up of atoms (elements) e.g. carbon,
oxygen, hydrogen, nitrogen, etc.
• When we eat, respire, feel happy, feel sad, etc. a! are chemical
activities.
• Chemicals keep us alive by reacting with each other.
• Common elements that form ce! are carbon, hydrogen and oxygen
(95% of ce!).
• Atoms combine and form molecules.
• Molecules are both organic and inorganic.
• Organic molecules are more important as they form long chain
molecules.
Importance
Biology helps us in understanding,
1. How our body is made.
2. What is a normal metabolism.
3. What are the metabolic abnormalities.
4. How ce!s can communicate.
5. How DNA controls ce!.
6. How to "nd new ways to "ght diseases, etc
-> Chemical Composition of Ce! :
• Biogenic elements or bioelements are those 25 elements out of
92 natura!y occurring elements which are found in living
organisms
• 16 out of 25 are found in human beings.
• Bio elements are divided into ;
1) Major elements (form 99% of the body) i.e carbon, hydrogen,
oxygen, nitrogen, phosphorus, calcium.
2) Minor elements (form less than 1% of the body) i.e. potassium,
chlorine, sulphur, sodium, etc.
3) Trace elements (form less than 0.01% of the body) i.e. iron,
copper, zinc, etc.
Acc to Book ;
• A! living organisms are structura!y composed of ce!s and living ce!
contains a living matter ca!ed Protoplasm.
• However, chemica!y it contains 70% to 90% of H2O.
• If the water is evaporated, the remaining mass of ce! is ca!ed
Dry Weight of ce!.
• It consists of many carbon containing long chain molecules ca!ed
Biomolecules which are the types of organic molecules.
• The compounds produced by living organisms are ca!ed biomolecules.
• The elements which are involved in the synthesis of biomolecules are
mainly six i.e. carbon, hydrogen, oxygen, nitrogen, phosphorus and
sulphur.
• The form approximately 98% of the biomolecules.
-> Fundamental types of Biomolecules :
Biomolecules can be divided into fo!owing groups according to their
structures and functions in ce!s and organisms i.e
1) Carbohydrates 4) Nucleic Acids
2)Proteins 5) Conjugated Molecules
3) Lipids
-> Condensation and Hydrolysis :
• Macromolecules: also known as Polymer, made from many repeating
units.
• Micro molecule; also known as Monomer, unit of polymer
• Both occurs in the presence of speci"c enzymes.
1) Condensation;
• When two monomer join together -H from one molecule and -OH from
other molecule combine to form water (water formation also occur in
Anabolism)
• A Polymer of two monomers is ca!ed Dimer.
• Polymers have more than two monomer.
• Condensation is also ca!ed Dehydration synthesis B/c water is removed
(dehydration) and bond formation (synthesis).
2) Hydrolysis;
• Reverse of condensation is breakdown of polymer into its monomer by
addition of H20.
• -H from water bind with one monomer and the -OH with other molecule
and monomers are detached from each other.
• Food digestion - by hydrolysis with speci"c enzyme
 Importance of Water ( H O)
• Water is the most abundant component in the living ce!.
• it’s amount varies from 70% to 90%
• Je!y"sh has exceptiona!y large amount of water around 99%
• it is the medium of life
• it takes part in many biochemical reactions like hydrolysis and is
raw material for photosynthesis.
• Water is a polar molecule -> It has partial negative charge on oxygen
and partial positive charge on the hydrogen atoms.
• The separation of electrical charges is ca!ed Dipole-> gives water
molecule very important properties.
• These properties make water, the best solvent and cradle of life.

1) Hydrogen bond : It is an intermolecular force of attraction formed

between two molecule one of which contain partia!y charge H+ and
other contain partial O- charge as present in water.
These charges attract two molecules, this force of attraction due to
H+ and O- is ca!ed Hydrogen bond.
Due to this Hydrogen bonding two molecules have fo!owing two types
of characters.
(a) Cohesion or Cohesive force of attraction:
• Cohesion is among the similar molecules to stick together.
• Due to hydrogen bonding -> to form a long chain of water molecule
• Water #ows freely due to cohesion
• Surface tension is also due to cohesion•
• Due to surface tension water can bear insect weight•

(b)Adhesive force of attraction or Adhesion:

• Adhesion is b/w the water molecule and other polar surfaces
• Due to hydrogen bonding and polar nature
• Adhesive force is between two dissimilar molecules.
• Capi!ary action is due to Adhesive forces of water.
• it can hold of the water molecules in the vessels and prevent them
from backward #ow.
2) High speci"c heat :
Speci"c heat of a substance is the amount of heat energy required to
raise the temperature of 1gm of that substance by 1C°
(e.g. 15C° to 16C°)
• The speci"c heat of water is high due to its polar nature and
hydrogen bonding between their molecules.
• It means water required high amount of heat to make changes in its
temperature or warm up.
• It works as temperature stabilizer for organisms and hence protect
protoplasm against sudden thermal charges.

3) High heat of vaporization :

• Amount of heat required to convert a unit mass into gaseous form
ca!ed Heat of vaporisation.
• Represented by calorie per gram or kcal/kg
• Water has high heat of vaporization ie: 574 kcal/ kg
• Greater the heat of vaporization higher wi! be the chances of stability
in state or vice versa.
• Water requires to absorb high heat to change its state from liquid to
vapours.
• It gives stability to water molecules and its state in ce!.
• It plays an important role in thermoregulation.
• It also provides cooling e$ect when evaporated during transpiration
are perspiration.
4) Hydrophobic exclusion :
• It is the tendency of water to coalesce oil drop into large droplet.
• The water molecules have hydrogen bonding between them which are
destroyed by the presence of hydrophobic oil and form new bonds.
• The water molecules then form more hydrogen bonds with themselves
and the nonpolar molecules clump together.
• This excludes hydrophobic substance (oil) from water.
• Eg : when a few drops of oil put on surface of water, a! the drops wi!
tend to coalesce (come together) into a single drop
• This property help in maintaining the integrity of lipid bi-layer
membrane.

5) Ionisation of water :
• The water molecules ionize into H+ and OH-
• This reaction is reversible and also maintain equilibrium.
• Due to ionization property water may behave as acid or base i.e.
Amphoteric in nature.
• It also behaves as bu$er due to this nature.
• It maintains pH for enzymatic activities in ce!s and organs.
6) Anomalous behaviour of water :
• Water shows di$erent behavior below 4°C.
• Usua!y matter contract at low temperature but due to hydrogen
bond below 4°C, water expands which decreases its density so at
0°C water expands maxima!y in ice condition.
• The low density water in ice become lighter, comes above the
surface of high density water of liquid.
• It makes the life possible under frozen water.

Carbohydrate ( Carbo -> carbon ) , ( Hydrate -> water )

• The literal meaning of word carbohydrate is hydrated carbon.

• This biomolecule contains C, H and O as element where the
hydrogen and oxygen are present in the simple ration of 2:1 as
present in water.
• The general formula of carbohydrate molecules is CnH2nOn,
whereas 'n' is the whole number.
• According to I.U.P.A.C carbohydrates are de"ned as
"the polyhydroxy carbonyl compounds", carbonyls are aldehydes or
Ketones.
• Main source of carbohydrates are plants because they synthesize
carbohydrate molecules as primary product during photosynthesis.
• Other bio-molecules are produced from carbohydrate during di$erent
metabolic pathways.
• They are sweet in taste if feels therefore ca!ed sacchrum or
Saccharide. Also ca!ed sugars.
• Carbohydrate found abundantly in a! organism, like ce!ulose in
ce! wa! of plant.
• It plays both structural and functional role.
a) Monosaccharides :
• The group of carbohydrate molecules which contain only one sugar
molecule.
• They cannot be hydrolysed further
• The empirical formula of their molecules is CnH nOn
• Colorless, crysta!ine, simplest, soluble in water.
• Monosaccharide can further be classi"ed on the basis of C atoms
present in them, the su$ix ‘Ose' is used with no: of C atoms present
in them as given in fo!owing table.

• Glycerose and Dihydroxy acetone are important trioses, produced

during respiration.
• Tetrose are rare in nature, it occurs in some bacteria
• Pentose sugar form basic skeleton of nucleic acid.
• Hexose are most important sugars from biological point of view.
1) Glucose -> found in ripe fruit, sweet corn and honey. It is also found
in a! known polysaccharide in combined state.
2) Fructose another hexose present in fruit so ca!ed fruit sugar
usua!y they are found in ring structures but we can also draw their
structure in open chain form.
Hexoses can be further divided into :
1) Aldohexose isomers -> ( having same molecular formula, but
di$erent the structural formula ) like glucose, galactose, mannos etc.
2) Ketohexose isomers -> like Fructose,Sorbose and Psicose.
b) Oligosaccharides :
-> Made up of 2 to 10 monosaccharides.
-> Comparatively less sweet in taste and less soluble in water
-> The most common type of is disaccharide, which yields two
monosaccharides.
-> Can be hydrolysed
-> The covalent bond between these two is the Glycosidic bond.
-> A glycoside is simply a ring shaped sugar molecule that is
attach to another molecule, the sugar ring may be either 5
membered ring or a six membered ring.
For example sucrose is a disaccharide, composed of two sugar units
a glucose and a fructose.
-> The disaccharide may be reducing or non-reducing sugar.
• The reducing sugar is any carbohydrate which is capable of being
oxidised and causes the reduction of other substances without
hydrolysis.
It is due to the presence of free aldehyde or free ketone group.
Examples are maltose, lactose etc.
• The non-reducing sugars are carbohydrate which are unable to be
oxidised and do not reduce other substance.
It is due to absence of free aldehyde or ketone groups, e.g. sucrose
or re"nose etc.
Living organisms especia!y plants transport their sugar from
source (leaf) to sink (fruit) tissues in the form of non-reducing
sugar where glycosidic bonds are formed between 'carbonyl' groups
of both sugars. Sucrose is the sugar which is non-reducing. It
contains more energy i.e, it is energy e$icient in transport and
storage. During transport it is not oxidized and react with other
substance so no intermediate reaction with other molecules occur.
C) Polysaccharide:
These are high molecular weight carbohydrates which on
hydrolysis, yield many monosaccharides. These are formed by the
condensation. yield many thousands of Monosaccharide units, e.g.
starch, glycoge" ce!ulose and chitin.
-> Starch ;
• Formed by the condensation of hundreds of a-glucose
• Storage carbohydrate of plant
• Mainly stored in root, stem and seed.
• Found in cereals, legumes, and other vegetables
• Digested in mouth + sma! intestine by enzyme Amylase
• Upon hydrolysis it yields Maltose and further by enzyme Maltase
and yield glucose.
• Gives blue colour with iodine solution
-> Glycogen ;
• Polymer of Alpha-glucose:
• Known as Animal starch: b/c stored form of food in animals•
• Stored in liver and muscle
• Digestion is similar to that of starch
• Gives red colour with iodine
• It is more branched than amylopectin
• Insoluble in water
• Also found in fungi and bacteria
-> Ce!ulose ;
• Most abundant carbohydrates on earth
• Polymer of hundreds of Beta-glucose
• Highly insoluble in water
• Structural carbohydrates of plant in ce! wa! of plants
• Paper —> pure form of ce!ulose:
• Digested by enzyme Ce!ulase which is absent in human being
• No color with iodine solution
• Have amylase like structure: Have B-1.4-glycosidic linkage
• glucose units are joined in the straight chain ( not branched )
which further coils and condenses to form tubes.
-> Chitin (C H O N)n ;
• 2nd most abundant on earth•
• Structural carbohydrate found in ce! wa! of fungi (known is
Fungal ce!ulose) and exoskeleton of arthropods
• It is derivative of N-acetyl glucosamine -> an amide derivative
of glucose.
• Un-branched structure like ce!ulose to which N-acetyl
glucosamine are attached,forming crysta!ine Nano "brils.
• linked by Beta=1.4-glycosidic linkage
• Functiona!y, it is comparable to Keratin protein.
• Chitin is modi"ed polysaccharide which contains Nitrogen which
a!ows for increased hydrogen bonding between adjacent polymers,
giving it more strength.
• In its pure and unmodi"ed form chitin is translucent, pliable,
resilient and quite tough in most arthropods .
• But it is mostly found in modi"ed form such as proteineceous
matrix form exoskeleton of insects, with CaCO; in the she!s of
mo!usks and crustaceans, composite material is much harder
and sti$er than pure chitin.

Stereoisomers in carbohydrates and its role in arti"cial sweetness

• Stereoisomer: in which -H and -OH are arranged at d/f pattern at

asymmetric carbons
• Stereoisomer number depends on asymmetric carbon atoms
by 2 where n represent the number of asymmetric carbon atom
• Asymmetric carbon atom: carbon atom bonded with four other
d/f atoms.
• Glucose has 16 isomers
• Most of the sugars in our body are right handed.
• The taste of right handed and left handed sugars are same
• Protein (Enzymes) are also right handed and left handed.
• The enzymes which are present in our body are also right handed
therefore right handed enzymes metabolize right handed sugars
only.
• They are unable to digest or metabolize left handed sugars.
• The arti"cial Sweetener which are used by diabetic patients
usua!y are left handed sugars, these sugars have same mass and
same sweetens but have zero calories.
• These sugars are not digested in our body because a! of our
enzymes are right handed and they are speci"c to break down the
right handed sugars.
• The left handed won't "t into catalytic site consequently there wi!
be no breakdown of these sugar, no metabolism and no calories.

Right handed sugar Left handed sugar

 Protein ( GR : Proteios -> first rank )
• Proteins can be de"ned as the polymers of amino acids
• Proteins are the most important organic compounds of the ce!
• They constitute major part of the dry weight of a ce!.
• Proteins are have C, H, O and N as elements, sometimes they
contains S also.
• Due to presence of N in large proportion they are ca!ed nitrogenous
compounds.
• Proteins are the building blocks of tissues.
• Many parts of the body such as hair, nails and feathers are also
protein.
• Whereas meat, "sh, milk and pulses are the major source of protein.
-> Amino acid as a building block of protein
• Proteins are macromolecule or polymers of amino acids.
• These amino acids are monomers and linked with each other by a
covalent bond ca!ed peptide bond or peptide linkage.
• Each protein has a unique sequence of amino acids that gives
the unique properties to these molecules.
• There are 20 basic amino acids which constitute each type of protein,
found in viruses to human beings.
• Contain at least one amino group -NH , which works as a base.
• Contains one carboxylic acid group - COOH , which works as an acid.
• At center there is carbon termed as Alpha-carbon ( asymmetric )
• The -R (Radical ) group is changed in every amino acid.
-> Formation and breakdown of peptide linkages ;
• Amino acids are linked together to form polypeptides or proteins
• The amino group of one amino acid may react with the carboxyl
group of another releasing a molecule of water.
• The linkage between the hydroxyl group of carboxyl group of one
amino acid and the hydrogen of amino group of another amino
acid release H20 and form C-N link, to form a bond ca!ed
Peptide bond/Amide linkage.
• The resultant compound has two amino acid subunits and is a
Dipeptide.
• A dipeptide has an amino group at one end and a carboxyl group
at the other end of the molecule.
• So both reactive parts are again available for further peptide
bonds to produce tripeptides, tetra-peptides, and penta-peptides
etc, leading to polypeptide chains
• The polypeptide chain can be broken by breaking peptide bonds by
the process of hydrolysis with the help of hydrolytic enzymes.
• The protein chain can be broken into sma! chain of more than
10 amino acids ca!ed peptone, whereas peptone can be hydrolysis
further into sma! units of few amino acid ca!ed peptide which are
further hydrolysis into amino acids.

-> Structure of Protein :

1) Primary structure -> sequence of amino acid in polypeptide
chain of protein.
2) Secondary structure -> due to the presence of hydrogen bonds,
polypeptide chains of protein require two di$erent shapes ;
Alpha helix and beta pleated sheets.
3) Tertiary structure -> you took the present of hydrogen bonds,
disulphide bonds, ionic interactions, and hydrophobic bond.
The polypeptide chain of protein requires a complicated 3-D
structure.
4) Quaternary structures -> two or more polypeptide chains of
protein
-> Signi"cance of the sequence of amino acid :
• F. Sanger was the "rst scientist who determined the sequence of
amino acids in a protein molecule.
• He found that Insulin is composed of 51 amino acid in two chains.
• One had 21 amino acid and other had 30 amino acids held
together by disulphide bonds.
• Same is found in Hemoglobin, which is composed of 4 chains, two
alpha (a) and two Beta (B) chains.
• Each alpha chain has 141 amino acids, while each beta chain
contain 146 amino acids.
• Human body has more than 10,000 protein
• Proteins are composed of speci"c and unique arrangement of
20 di$erent amino acid , determined by the sequence of
nucleotide on DNA.
• The sequence of amino acid is important for proper functioning.
• If the sequence is changed by single a a it cause disorder eg
Sickle ce! anemia.-> abnormality due to change in one amino
acid out of 574 amino acids.
• Normal RBC ce! shape = Disc shape:
• In sickle ce!. the amino acid Glutamic acid is replaced by
Valine at position No # 6 of ß chain•
• Sickle ce! can't carry oxygen
• Sickle ce! anemia is hereditary disease
-> Classi"cation of proteins :
Fibrous protein Globular protein
• long "bres of proteins • Spherical or E!ipsodial
• Insoluble in water • Soluble in salt, acid, or
• elastic in nature base or alcohol.
• Non-crysta!ine • Can be crysta!ised
• Perform structural role • Perform functional role
• Eg; Silk, Keratin, myosin • Eg; enzyme, antibodies,
spiderweb, "bres and clothing hormone, haemoglobin
 Lipids
• Lipids are the important diverse group of biological molecules,
widely distributed among plants and animals.
• The term lipid is proposed by Bloor in 1943, for those biomolecules
which are insoluble in water and soluble in organic solvents like ether
and alcohol etc.
• These compounds are made up of C, H, O like carbohydrates but
contain much lesser ratio of oxygen than carbohydrates
e.g. stearin is a fat, has molecular formula (C H O ).
• Due to high quantity of carbon and hydrogen, they contain almost
double amount of energy than carbohydrates.

1) Acyl glycerol ( Fats and oil ) :

• These are the condensation product of glycerol and three fatty acid
molecules commonly ca!ed fats and oils.
• They can be de"ned as the esters of glycerol and fatty acid.
• Ester is the bond or linkage formed between alcohol and organic
acid by removing water, this reaction is ca!ed esteri"cation.
• When three fatty acid combine with glycerol -> Triglycerol
(triglyceride) is formed.
• The triglycerol are neutral in nature
• Acyl glycerol provide energy for di$erent metabolic activities and
are very rich in chemical energy, twice in amount of energy content
than carbohydrate.
• It is estimated that a person of average size contains approx:
16 kg of fats which contain 144 × 10 KCal of energy.

Saturated Acylglycerol Un- Saturated Acylglycerol

• Saturated fatty acid • UnSaturated fatty acid
• Aka -> Fats • Aka -> oils
• Don’t contain any double • contain one or more double
bonds. eg : Stearin bonds. eg : Linolin in seeds
• Stable, physical state
 2) Phospholipids :
• Condensation, product of Glycerol + 2 fatty acid + 1 Choline
+ 1 phosphate.
• Consists of Polar head ( Hydrophilic -> water loving ) and a
Non-polar (hydrophobic) tail.
• Due to this amphiphilic
character it is the main
component of a! ce! membrane
• They are related to vital
functions such as regulation
of ce! permeability and
transport process.

3) Waxes :
• Highly hydrophobic ( Non-polar)
• Ester of one fatty acid and one long chain alcohol.
• Chemica!y inert and resistant to atmospheric oxidation
• Simple lipids -> found as protective coating
• May be natural or synthetic
• Bee's wax - in honeycomb
• Lanolin -> from sheep wool
• Cutin -> leaf surface of plants.
• Suberin - in ce! wa! of endodermis
• Synthetic waxes, genera!y derived from petroleum or polyethylene.
• Have considerable commercial importance.
 4) Terpenoids : Made up of isoprenoid units ( C H ).
• Found in ce! membrane as cholesterol, as pigment like.
chlorophy!, fragrance as menthol etc.
• Terpenes, steroids, carotenoids and prostaglandins are types
of Terpenoids.
Terpenes
• Contain few isoprenoid units like diterpens, Triterpens.
• These sma! size terpens are volatile in nature and produce
special fragrance.
• Some of these are used in perfume e.g. Myrcens from oil of bay,
Geranoil from rose, Limonene from lemon oil, Menthol from
peppermint oil.
• Some component of vitamin As, and A2, chlorophy! molecules and
some other molecules which are utilized in the synthesis of
rubber and latex.

Steroids
• Form steroid nucleus made up of isoprenoid units which contain
17 Carbon atoms arranged in four attached rings, 3 of them
are hexagonal and 1 is pentagonal in shape.
• The radical attached with them as side chains distinguish them
from one another cholesterol is one of the type of steroid.
• Cholesterol is the precursor for the synthesis of a number of
steroids i.e. testosterone, progesterone and estrogens.
 Carotenoids
• It is a poly terpene , consisting of long chain of isoprenoid unit
which contain isoprenoid rings at both or at one terminal.
• These compounds are pigments producing red, orange,
ye!ow and brown color in plants. Some important carotenoids
are plant pigments, like chlorophy!, cytochromes,
phytochromes, latex, rubber etc.

Prostaglandins
• A group of lipids made by mammalian tissues at the sites of
tissues damage or infection that are involved in dealing with
injury and i!ness.
• They control di$erent physiological process such as
in#ammation, intensity of sensation of pain, blood #ow, and
formation of blood clots, Immunity and the induction of labour.
• We use aspirin to reduce fever and decrease pain depend on the
inhibition of prostaglandin synthesis.
 Nucleic acid
• Founded by Friedrich Miescher a Swiss physician -> isolated a new
compound from the nucleus of pus ce!s, named it "Nuclein" it was
found that the it had acidic properties and hence it was renamed
nucleic acid.
•The nucleic acids are polymers of "ve sugar based compound ca!ed
nucleotide.
• These polymers have high molecular weight.
• These are present in a! living things from virus to man.
• There are two kinds of nucleic acids
i.e. Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA).
• Both nucleic acids are linear unbranched polymers.
• DNA is the polymer of Deoxyribonucleotide and RNA is the polymer
of Ribonucleotide.
-> Composition of nucleotide ;
• The nucleotide without phosphate
ca!ed Nucleoside.
-> Mono-nucleotide :
• These mononucleotide have extra phosphate group as ADP
(Adenosine phosphate) or ATP as (Adenosine Tri Phosphate).
• ATP work as energy storing, carrying and energy providing
molecules to metabolic reactions.
• This energy is utilized to derive energy demanding reactions.
• During conversion of ATP into ADP, 7.3 Kcal/ mole or 31.81 kj/ mole
energy is released.

-> Dinucleotide :
• Sometimes two nucleotides are covalently bonded together to form
a compound ca!ed dinucleotide.
• Eg ; NAD (Nicotineamide Adenosine Dinucleotide).
• A vitamin Nicotine is attached with these two nucleotides in NAD.
• It works as co-enzyme for Redox reaction.
• It carries 2e (electron), 2H+ (proton) and energy
e.g. NADH2, FADH2 etc.
-> Formation of phosphodiester bond
• The two nucleotides are linked together by a bond in nucleie acid i.e.
DNA or RNA, this linkage or bond is ca!ed phosphodiester bond.
• It is considered as the backbone of the nucleic acid strands.
• It is a bond which is formed as a result of the condensation reaction
between phosphate group (PO ) group of pentose sugar.
• So it is de"ned as a chemical bond that forms when exactly two
hydroxyl group, one in a phosphoric acid reacts with a hydroxyl of
another molecules of sugar forming ester bond.
• In this bond the 3'-carbon of pentose sugar is linked with 5' carbon in
DNA or RNA via phosphoester bond and thus it acts as backbone.
• These are the bonds that hold the sugar phosphate components of the
DNA molecule together.
-> Polynucleotide
• Nucleotides are joined together and form polymers like DNA and RNA.
• They have variety of role in living organism.
• DNA performs function of transformation and heredity Genetic
information is encoded in DNA in simple fashion in the form of codes.
-> Structure of DNA
• Structure of DNA was explained by James Watson and Francis
Crick in 1953 by making model.
• They proposed that ;
1) The DNA is a double helical structure.
2) Each helix is made up of 4 types of Nucleotides.
3)Both helix are complementary to each other i.e. if one helix
contain A the opposite or complimentary helix wi! contain T
whereas (C) is complementary to(G).
4) Each helix is consist of 2 parts ;
(i) Upright: made up of deoxyribose sugars and phosphate
(ii) Rung: made up of Nitrogenous bases.
• Both helix are held together by H-bond due to which zipping ( DNA
polymerase ) in 5’ to 3’ direction in fragments which are joined by
( DNA ligase ) and unzipping of both helix ( DNA Helicase ) occur by
making and breaking of there bonds.
• Both helix are opposite in direction i.e. one chain run from 5' to 3'
end (downward) whereas the other chain runs from 3' to 5' end
(upward)direction.
• Distance between two helix remain same from one end to another
end i.e. 20 A°.
• Each turn of the duplex consist of 10 base pairs.
Gene -> DNA is a heredity material it carries genetic information
from parent to o#spring in the form of Genes.
• A gene is a part of DNA which has information to synthesis a
protein, which wi! work as enzyme.
• It is a functional unit of heredity material.
• The gene gives instructions for developing characters like eye
and hair color by producing enzymes.
• Genetic information $ow in a ce! from DNA to m RNA than to
cytoplasm in two steps for protein synthesis
 Protein synthesis ( Active process )

Transcription Translation
• Occurs in the nucleus • Occurs in the cytoplasm
• Gene is used to make mRNA • mRNA attaches to ribosome
• It requires activated • tRNA and rRNA translate the
nucleotide so that the information of mRNA into
nucleotides can have speci"c sequence of amino
su$icient energy. acid, which helps to synthesise
• It requires RNA polymerase the protein.
 RNA ( Ribo nucleic acid )
• RNA is also a polymer of nucleotides.
• Made up of ribose sugar
• Single stranded
• it is a polymer of ribonucleotide i.e. the nucleotide contain ribose
sugar and one of the nitrogenous bases i.e. A, G, C and U.
• It means instead of Thymine it contains the nucleotide of uracil.
• DNA is a heredity material while RNA helps in protein synthesis.
There are three types of RNA.
(i) Messenger RNA (mRNA) :
• It consists of single strand except in some viruses it is double
• Its length depends on the size of gene.
• It contains information in the form of Genetic codes, CODON.
• These codons are basica!y triplets of Nucleotides of mRNA which
encode one amino acid.
• It is about 3 to 4 % of total RNA in the ce!.
(ii) Transfer RNA (tRNA) :
• The sma!est sized RNA consists of only 70 to 90 nucleotides.
• it is single stranded RNA shows duplex at some regions where
complementary bases are present.
• It has anticodons of genetic codes as its complementary form.
• It transfers related amino acid from cytosol to ribosome, they are
60 in numbers, while human ce! contains only 45 di#erent types of
tRNA.
•It is about 10 to 20% of total RNA.
(iii) Ribosomal RNA (rRNA) :
• rRNA is present in ribosome.
• It has largest size among a! three RNA
• 80% of total of RNA in a ce! is rRNA.
• It is involved in peptide linkages during protein synthesis.

-> Conjugated molecules :

They are formed when biomolecules of two di$erent groups combine
chemica!y with each other acting as one Unit.
These are glycolipids, glycoproteins, lipoproteins and Nucleoproteins.
(i) Glycolipids or Cerebrosides:
• These are conjugates of lipids and carbohydrates.
• They are also ca!ed cerebrosides because they are present in white
matter of brain and myelin sheath of nerve "ber.
• They are also found in the inner membrane chloroplast.
(ii) Glycoproteins or Mucoids:
• They are formed by combining a molecule of carbohydrate with a
protein molecule.
• Most of the oligo and polysaccharide in animal and plant ce!s are
linked covalently to protein molecules.
• They perform function as, transport proteins, receptors, antigens of
blood group etc.
• It is one of the part of egg albumin and gonadotropins.
(iii) Lipoprotein:
• They are conjugate of lipids and proteins.
• They help in the transportation of lipids in blood plasma.
• They also occur as component of membrane of mitochondria,
endoplasmic reticulum, nucleus, egg yolk and chloroplast
membrane.
(iv) Nucleoprotein:
• They are formed by simple basic protein and nucleic acid
• They are the main component of chromatin material, chromosomes
ribosomes.