CONCEPT BIOMOLECULES

Biomolecules are the molecules or chemicals that are present in the living organisms. Biomolecules may be inorganic
such as minerals,water or organic such as carbohydrates, fats, proteins, nucleic acids, etc. Different biomolecules
MAP perform different functions in living organisms. Some biomolecules act as universal genetic material, e.g., nucleic
acid (DNA). Some biomolecules are involved in the maintenance and metabolic processes of living organisms, e.g.,
proteins, carbohydrates.

Enzymes Carbohydrates
These are proteinaceous substances that acts as catalyst in living organisms, Carbohydrates are most abundant biomolecules on earth. These are
regulating the rate at which chemical reactions progress without itself composed of carbon, hydrogen and oxygen. The general formula is
being altered in the process e.g, maltase. G,(H,0), or (CH,0)n. Living organisms use carbohydrates as accessible
energy to fuel cellular reactions.
Action
Lock-and-key model Monosaccharides
This theory explains how the enzyme remains unaffected at the Enzyme
Simple carbohydrate CH,OH
end of chemical reaction. monomers which cannot
H H
of be hydrolysed into
Substra Modes Smaller components, OH H
HO
e.g., glucose.
General formula : H
Active site Glucose

Enzyme Oligosaccharides
Enzyme substrate
complex Small carbohydrate chains containing 2-10 monosaccharide
units. E.g., Sucrose
CH,OH
Induced-fit model H H CH,OH H

According to this model, the enzyme's active site is made of two HC

OH H OH
components : catalytic group and buttressing group. CH,OH
H OH H
Sucrose
SubSt

-Catalytic group Polysaccharides

Buttressing
group Polysaccharides are most abundant carbohydrates found
in food. They are formed by polymerisation of large
Enzyme Enzyme number of monosaccharides. They are of two types
substrate
complex
() Homopolysaccharides - Formed by polymerisation of only
one type of monosaccharide monomer, e.g.. glycogen, cellulose,
(i) Heteropolysaccharide - Formed by condensation of two
or more types of monosaccharides or their derivatives, e.g.,
Primary metabolites Heparin.
CH,OH CH;OH
Some of the organic compounds like carbohydrates, fats, proteins,
nucleic acids, etc., are required for basic metabolic processes H
H
and are directly involved in normal growth, development and OH OH
reproduction. H

H HN CH; HN CH
Secondary metabolites
Many plants, fungi and microbes of certain genera synthesise Jn
a number of organic compounds which are not involved in B-(1, 4)-N-acetyl-D-glucosamine (Chitin)
primary metabolism (photosynthesis, respiration, protein and
lipid metabolism) and seem to have no direct function in growth
and development of organism, e.g., gum, resin, rubber, etc. Metabolites
Types :(i) Isoprenoids or terpenoides, e.g., rubber, steroids,
carotenoids. (i) Nitrogen containing compounds, e.g., Metabolites are the intermediate products of metabolic reactions catalysed <*
by various enzymes that naturally occur within cells.
alkaloids, glycosides, glucosinolates. (ii) Phenolic compounds,
e.g, tannins, flavonoids, lignin, etc.
 Proteins
Secondary structure
Polypeptide chain is coiled to form a complex structure.
Proteins are the most diverse biomolecules on earth. These are variously It is maintained by hydrogen bond between amide
folded linear polymers of amino acids. Linear chains of amino acids are hydrogen and carbonyl oxygen of the peptide backbone.
linked by peptide bonds and are called polypeptides. Proteins perform
various structural and physiological functions in living beings. H,N-(
Primary structure
Hydrogen
Basic structure of a protein. R.
H
H--R bond
-N
Jo.--f-
H
Poly
OH -N peptides
CH,COOH
HX 0 H HR8 B-Pleated
SH CH, NC N

CH,0H CH CH, CH, R6 -helix

Fig.: Secondary structures of proteins
-HN - CH- CO-NH - CH - CO-NH CH-CO NH H- CO
Fig.: Primary structure of aprotein. Nand Crepresent its first and last termini. Tertiary structure
Heme
It represents the
Quarternary structure rearrangement of
Some proteins are made up Heme group secondary structure into
of more than one amino acid final 3-dimensional shape
chain, giving them a quaternary
structure.
Example - Haemoglobin Fig.: Tertiary structure of
protein myoglobin
Fig.: Quaternary structure of haemoglobin
showing four polypeptide chains- two DNA
a-chains and two B-chains
> It isa helically twisted double chain.
> It is the geneticC material.
Nucleic Acids 3

CH,
These are formed by end toend polymerisation of large number of repeated Thymine : : : : : Adenine

units called nucleotides. Anucleotide contains - a nitrogen base, a pentose

sugar and phosphate group. The function nucleic acid is to store and 0--0H
OH
express genetic information. HO- 0

RNA CH.
GuanineEE ytosine
Single stranded:
> Mainly of three types : - mRNA, RNA and tRNA.
> It is genetic material of some viruses.
Fig.: Diagram indicating secondary structure of DNA

Lipids Simple lipids

Lipids are made up of glycerol and fatty acids. Glycerol is made up of Esters of fatty acid and glycerol. E.g., (i) Fats and oils :
three carbon atoms with a hydroxyl group attached to it and fatty acids These are triglycerides because they are esters composed
consists of an acid group at one end of a hydrOcarbon chain. Fatty acid may of three fatty acids joined to glycerol. Fats are solid at room
be saturated (no double bond) or unsaturated (one or more double bonds). temperature whereas oils are liquid at room temperature.
(iüi) Wax :Wax is an ester of long-chain alcohol and a
Derived lipid fatty acid.
These are derived from CH, CH, CH, CH, Compound lipid
the hydrolysis of simple CH Esters of fatty acid with
and compound lipids. They CH, alcohol but contain extra
include fatty acids, glycerol, CHg CH-0-(-R,
groups in addition to
sphingosine and steroid CH,
alcohol and a fatty acid.
derivatives. (i) Steroids : CH,-0-(-R,
These are derived lipids. Eg. ()Phospholipids
HO : That yield fatty acids,
These may be recognised Cholesterol glycerol, amino alcohol Hy-0p- CHy-CH; N-CH
by their cyclopentano spingosine, phosphoric OH
CH3
perhydrophenanthrene ring tetracyclic skeleton. (i) Sterols : These acid and nitrogen Lecithin
are subgroups of steroids with a hydroxyl group at the 3-position of containing upon hydrolysis. (i) Glycolipids : That yield
the 15 ring. acids glycerol and a carbohydrate upon hydrolysis.