9 Biomolecules

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BIOMOLECULES-CLASS XI BIOLOGY 1

BIOMOLECULES

BIOMOLECULES

PREPARED BY S RATH PGT BIO K V III BBSR http://students-learn.blogspot.com/

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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

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Classification of

Biomolecules

BIOMOLECULES

MICROMOLECULES

Mol. Wt.< 1000

MACROMOLECULES

Mol. Wt. >1000

Amino acid nucleotides

Sugars , lipids

Polysaccharides, proteins

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BIOMOLECULES-CLASS XI BIOLOGY 4

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,

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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

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lipids

lipids

Straight chain compound

Fused hydrocarbon Ring 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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BIOMOLECULES-CLASS XI BIOLOGY 12

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.

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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.

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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.

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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.

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BIOMOLECULES-CLASS XI BIOLOGY 22

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Factors affecting enzyme

action

 Temperature  pH  Substrate concentration  chemicals

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Effect of substrate concentration velocity

(s) Vmax

Figure

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