Q1. Select the most appropriate statements about human insulin. (I) Human insulin is made up of two short polypeptide chains. (II) The two chains are A and B chains. (III) The two chains are α and γ chains. (IV) Pro-hormone contains an extra stretch of C-peptide. (V) C-peptide is present between the two chains in the mature form of human insulin. Choose the most appropriate answer from the options given below:
Explanation
Mature human insulin consists of two short polypeptide chains, named the A chain and the B chain, joined by disulphide bonds. Hence the first two statements are correct. Insulin is first produced as proinsulin, a pro-hormone that has an additional C-peptide segment connecting the two chains; that makes the fourth statement correct. The chains are not called α and γ chains, so the third statement is wrong. In mature insulin, C-peptide is removed, so the fifth statement is also wrong. The set containing I, II and IV only is therefore correct.