Which statement best describes insulin synthesis?

Which statement best describes insulin synthesis?

• A. Insulin is synthesized from proinsulin
• B. Insulin is synthesized by alpha cells
• C. C-peptide is the active form
• D. Two-chain polypeptide is not a feature of insulin

Answer: (A)

Insulin synthesis involves processing a larger precursor into the mature hormone. In the pancreatic beta cells, insulin is produced first as preproinsulin, which is then converted to proinsulin. Proinsulin is processed by removing a segment called the C-peptide and splitting the molecule into two linked chains, A and B, forming mature insulin. This shows that insulin is synthesized from proinsulin, with C-peptide released along with insulin as a byproduct. Notably, insulin comes from beta cells, not alpha cells (which produce glucagon). C-peptide is not the active hormone itself—it's a byproduct that helps indicate endogenous insulin production. And mature insulin is indeed a two-chain polypeptide (A and B chains connected by disulfide bonds), so stating that it is not a two-chain entity would be incorrect.

Insulin synthesis involves processing a larger precursor into the mature hormone. In the pancreatic beta cells, insulin is produced first as preproinsulin, which is then converted to proinsulin. Proinsulin is processed by removing a segment called the C-peptide and splitting the molecule into two linked chains, A and B, forming mature insulin. This shows that insulin is synthesized from proinsulin, with C-peptide released along with insulin as a byproduct.

Notably, insulin comes from beta cells, not alpha cells (which produce glucagon). C-peptide is not the active hormone itself—it's a byproduct that helps indicate endogenous insulin production. And mature insulin is indeed a two-chain polypeptide (A and B chains connected by disulfide bonds), so stating that it is not a two-chain entity would be incorrect.