Question

In mature insulin, which of the peptide is not present?

• A. C-peptide
• B. A and B peptides
• C. A-peptide
• D. B-peptide

Hint:

C-peptide is removed during insulin maturation, serving as a marker of insulin production rather than being part of the active molecule.

Answer 1

The Correct Option is A

• Definition of Insulin: Insulin is a hormone composed of A and B peptide chains linked by disulfide bonds, formed after processing of proinsulin.
• Option Analysis:
  • (1) C-peptide: Proinsulin contains A, B, and C peptides; during maturation, the C-peptide is cleaved and removed, leaving only A and B peptides in mature insulin. This is correct.
  • (2) A and B peptides: These are the active components of mature insulin. This is incorrect.
  • (3) A-peptide: This is part of mature insulin. This is incorrect.
  • (4) B-peptide: This is also part of mature insulin. This is incorrect.
• Mechanism Insight: The C-peptide is excised by proteases during insulin maturation, and its presence indicates proinsulin, not the active hormone.
• Conclusion: The correct answer is (1) C-peptide, as it is absent in mature insulin.