9 Biomolecules

BIOMOLECULES

PREPARED BY S 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

MICROMOLECULES Mol. Wt.< 1000 Amino acid nucleotides Sugars , lipids

MACROMOLECULES Mol. Wt. >1000 Polysaccharides, proteins Nucleic 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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lipids lipids

Straight chain compound

simple

Fused hydrocarbon Ring e.g. cholesterol

compound

oil

phospholipids

fats

glycolipids

waxes BIOMOLECULES-CLASS XI BIOLOGY

sphingolipids

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Nucleotides  

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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  

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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 

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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  

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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 

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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 Cterminal a. a.

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Secondary structure of protein 

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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 

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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 

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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 

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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 

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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

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BIOMOLECULES-CLASS XI BIOLOGY Activation energy requirement

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Factors affecting enzyme action    

Temperature pH Substrate concentration chemicals

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Vmax

velocity

(s) XI BIOLOGY Effect of substrate BIOMOLECULES-CLASS concentration

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