9 Biomolecules

BIOMOLECULES-CLASS XI BIOLOGYBIOMOLECULES-CLASS XI BIOLOGY 11

BIOMOLECULESBIOMOLECULES

PREPARED BYS RATH PGT BIO K V III BBSR

http://students-learn.blogspot.com/

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Biomolecules of cells All carbon compounds that are found in

the living tissues are called Biomolecules. Example-carbohydrate, fat, protein, amino

acids, lipids etc.

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Classification of Biomolecules

BIOMOLECULES

MICROMOLECULESMol. Wt.< 1000

MACROMOLECULESMol. Wt. >1000

Amino acid nucleotidesSugars , lipids

Polysaccharides, proteinsNucleic acids

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Amino acids

These are organic compounds which contain an amino group and an acidic group .

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 R group.

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Amino acids

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.

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Types of amino acids

Basic – lysine arginine Acidic – glutamic acid aspartic acid Neutral – alanine glycine valine Aromatic – phenyl alanine , tyrosine,

tryptophan

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Sugars

Simplest sugars are monosaccharides, which cannot be hydrolysed further composed of 3-7 carbon atoms. E.g. glyceraldehydes, ribose, glucose, fructose etc.

They have either free aldehyde or ketone group which reduce cupric ion to cuprous ion ,called reducing sugar.

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Sugars

Oligosaccharides may have two or a few monosaccharides.

Bond between two monosaccharides is called glycosidic bond.

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lipidslipids

Straight chaincompound

Fused hydrocarbonRing e.g. cholesterol

simple compound

oil phospholipids

fats

waxes

glycolipids

sphingolipids

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Nucleotides 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.

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Primary and secondary metabolites

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.

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Polysaccharides 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

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Proteins 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.

There are 4 levels of protein structure.

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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.

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Secondary structure of protein

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.

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Tertiary structure of protein

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.

E.g. amylase, pepsin and other enzymes.

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Quaternary structure of protein

When a protein has many sub units, each having primary, sec. And tertiary st. of its own, the protein is said to be quaternary.

E.g. haemoglobin, insulin

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Enzymes 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.

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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.

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Classification of enzyme Oxidoreductase Transferase Hydrolases Lyases Isomerasees ligases

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Mechanism of enzyme action

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 22Activation energy requirement

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Factors affecting enzyme action Temperature pH Substrate concentration chemicals

BIOMOLECULES-CLASS XI BIOLOGY 24Effect of substrate concentration

velocity

(s)

Vmax