Question

Which of the following statements regarding the structure of proinsulin and mature insulin are not correct?
(i) Proinsulin is made up of three polypeptide chains A, B, and C.
(ii) C-polypeptide chain with 33 amino acids is removed prior to insulin formation.
(iii) Mature insulin is made up of 51 amino acids and arranged in two polypeptide chains-A and B.
(iv) Polypeptide chain A has 30 amino acids and polypeptide chain B has 21 amino acids.
(v) Polypeptide chains A and B are interconnected by only one S-S linkage.

• A. (i) and (ii)
• B. (iii) and (iv)
• C. (iv) and (v)
• D. (iii), (iv) and (v)

Answer 1

The correct option is C (iv) and (v)

Human insulin is made up of 51 amino acids arranged in two polypeptide chains: A, having 21 amino acids and B, with 30 amino acids. The two polypeptide chains are interconnected by two disulphide bridges. The two polypeptide chains are interconnected by two disulphide briges. The hormone develops from a storage product called pronsulin. Proinsulin has three chains: A, B and C, C-chain with 33 amino acids is removed prior to insulin formation.

So, the correct answer is '(iv) and (v)'.