What are proteins ?

Explanation

Proteins are the complex nitrogeneous compounds formed by the combination of large number of `alpha`-amino acids which are linked by peptide bonds (-CO-NH-). Thus, proteins are polypeptides in nature. The polypeptides with molecular mass more than 10,000 a.m.u. are called proteins.
Proteins can be classified into two types on the basis of their molecular shape.
Fibrous proteins : When the polypeptide chains run parallel and are held together by hydrogen and disulphide bonds, then fibre-like structure is formed. Such proteins are generally insoluble in water. Some common examples are keratin (present in skin, hairs, nails) collagen (in tendons), fibron in (in silk), myosin (in muscles) etc.
(b) Globular proteins : This structure result when the chain of polypeptide coil around to give a spherical shape. These are generally soluble in water. Insulin and albumins are common example of globular proteins.