C peptide is present in:

The correct answer is Option (3) → Pro-insulin

In humans, insulin is first made as a pro-hormone, called pro-insulin. It has three parts: chain A, chain B and an extra stretch between them, the C peptide. During maturation the C peptide is removed. The mature hormone has only chains A and B, joined by disulphide bridges.

(1) Mature insulin — Incorrect. The C peptide has already been cut out of it. Only chains A and B remain.

(2) Hemoglobin — Incorrect. It is built from globin chains and haem. It has no C peptide.

(3) Pro-insulin — Correct. It is the form that carries the C peptide.

(4) Collagen — Incorrect. It is a structural protein of connective tissue and has nothing to do with insulin.

NCERT Extract:
Genetically Engineered Insulin – …