Proteins are the most diverse chemicals of the living system. They are macromolecules made up of amino acids joined together by peptide bonds. The minimum molecular weight of a protein is 4500 (adrenocorticotrophin hormone) with 39 amino acids, 5733- 5808 (insulin, two polypeptides, 51 amino acids, chain A of 21 amino acids and chain B of 30 amino acids) and 6000 (bacterial ferredoxin).