Write notes on proteins.

1.	Write notes on proteins.
Answer» Proteins are polypeptide chains of amino acids . Classification of proteins : proteins can be classified into two type on the basis of their molecular shape. a) Fibrous proteins : These are fibre like proteins, the polypeptide chains are parallel which are held together by hydrogen and disulphide bonds. these are insoluble in water . Ex. Keratin present in hair, wool silk etc, and myosin in muscles. b) Globular proteins : In these proteins , the polypeptide chains coil around to give a spherical shape. these are soluble in water . Ex. : Insulin and albumin. The structure of proteins is explained in four different levels. a) primary structure b) secondary structure c) tertairy structure d) quaternary structure Protein Denaturation : The phenomenon of disorganization of native protein structure is known as denaturation . Denaturation results in the loss of secondary , tertiary and quaternary structure of proteins. This involves a change in physical, chemical and biological properties of protein molecules. Agents of denaturation : Physica agents - heat , violent shaking , X - rays , UV - radiation Chemical agents - Acids, alkalies, organic solvents, urea , salt of heavy metals.

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