BIOMOLECULES-CLASS XI BIOLOGY 1
BIOMOLECULESPREPARED BY S RATH PGT BIO K V III BBSR http://students-learn.blogspot.com/
BIOMOLECULES-CLASS XI BIOLOGY 2
Biomolecules of cells
All carbon compounds that are found in
the living tissues are called Biomolecules.
Example-carbohydrate, fat, protein, amino
Mol. Wt.< 1000
Mol. Wt. >1000
Amino acid nucleotides
Sugars , lipids
BIOMOLECULES-CLASS XI BIOLOGY 4
These are organic compounds which
contain an amino group and an acidic
They are substituted methane with 4
substituent groups occupying the 4
valency positions of the carbon; these
are hydrogen, carboxyl group, amino
group & a variable group designated as
There are 20 amino acids occur in protein.
A specific characteristic property of amino
acids is the ionizable nature of amino and
carboxyl group, so the structure of amino
acids changes in solutions of different pHs.
BIOMOLECULES-CLASS XI BIOLOGY 6
Types of amino acids
Basic – lysine arginine
Acidic – glutamic acid aspartic acid
Neutral – alanine glycine valine
Aromatic – phenyl alanine , tyrosine,
Simplest sugars are monosaccharides,
which cannot be hydrolysed further
composed of 3-7 carbon atoms. E.g.
glyceraldehydes, ribose, glucose,
They have either free aldehyde or
ketone group which reduce cupric ion to
cuprous ion ,called reducing sugar.
BIOMOLECULES-CLASS XI BIOLOGY 8
Oligosaccharides may have two or a few
Bond between two monosaccharides is
Straight chain compound
Fused hydrocarbon Ring e.g. cholesterol
simple compound oil phospholipids fats waxes glycolipids sphingolipids
BIOMOLECULES-CLASS XI BIOLOGY 10
Organic compounds with heterocyclic rings. A nucleotide consists of a nitrogenous base, a
pentose sugar and a phosphate group.
A nucleoside has a nitrogenous base attached to a pentose sugar.
The nitrogenous bases are called adenine, guanine, thymine, cytosine and uracil
Polymerised nucleotides form DNA and RNA which are the genetic material.
Primary and secondary
Metabolites may be primary or secondary type. Primary metabolites have identifiable functions
and play specific roles in the normal physiological processes. E.g. amino acids, nitrogenous bases, nucleic acids etc.
Secondary metabolites are products of certain
metabolic pathways. E.g. pigments, rubber, gums, resins, carotenoids etc.
BIOMOLECULES-CLASS XI BIOLOGY 12
These are a class of organic compounds
(carbohydrates) which are long chain polymers of monosaccharides.
They are of two types: homopolysaccharides, heteropolysaccharides
Homopolysaccharides- cellulose, starch, inulin Heteropolysaccharides- chitin
They are heteropolymers containing a string or strings of amino acids.
A peptide bond formed between the carboxyl
group and the amino group of successive amino acids, joins the amino acids together.
Proteins result from the 20 amino acids , depending on the no.of amino acids and sequence of amino acids.
BIOMOLECULES-CLASS XI BIOLOGY 14
Primary structure of protein
Protein exists as a long chain of amino acids arranged in a particular sequence.
It is nonfunctional.
Position of amino acid in a protein is obtain from this.
1st a. a is called N-terminal and last is called C-terminal a. a.
Secondary structure of
There is interaction between every fourth a. a by formation of hydrogen bond. The
polypeptide has a helical shape. E.g. keratin. Only right handed helix are formed.
If two or more chains are held together by
intermolecular hydrogen bonds, the structure is called pleated sheet. E.g. silk fibres.
BIOMOLECULES-CLASS XI BIOLOGY 16
Tertiary structure of
When a polypeptide chain becomes further stabilised by folding and coiling by the
formation of ionic or hydrophobic bonds or disulphide bridges, the protein is said to be tertiary structure.
Quaternary structure of
When a protein has many sub units, each
having primary, sec. And tertiary st. of its own, the protein is said to be quaternary.
BIOMOLECULES-CLASS XI BIOLOGY 18
They are proteins that catalyse biochemical reaction, so called biocatalysts.
Specific for their substrate.
Each enzyme require a specific (optimum) pH & temp.
Accelerate a reaction by reducing the activation energy.
Nomenclature of enzyme
Named by adding the suffix ‘ase’ to the substrate. E.g. sucrase
According to the physiological activity it catalyses. E.g. oxidase, dehydrogenase
The source from which they are obtained. E.g.papain from papaya.
BIOMOLECULES-CLASS XI BIOLOGY 20
Classification of enzyme Oxidoreductase Transferase Hydrolases Lyases Isomerasees ligases
Mechanism of enzyme
Three dimensional structure of enzyme has one or more active site where the substrate binds.
Active site acts as ‘ lock’ into which substrate fits in like a ‘key’.
The point where substrate binds is called ‘substrate binding site’.
Substrate binding causes lowering of activation energy & reaction to proceed at a faster rate.
Binding of substrate induces the enzyme to alter its shape and fit more tightly.
Breaking of chemical bond of substrate and formation of E-P complex.
Enzyme releases product and free enzyme take up another molecule.
BIOMOLECULES-CLASS XI BIOLOGY 22
Factors affecting enzyme
action Temperature pH Substrate concentration chemicals
BIOMOLECULES-CLASS XI BIOLOGY 24
Effect of substrate concentration velocity