C-peptide of human insulin is

Options

A. a part of mature insulin molecule
B. responsible for formation of disulphide bridges
C. removed during maturation of pro-insulin to insulin
D. responsible for its biological activity

Answer

**Step-by-Step Solution:**

1. **Understanding Insulin Structure**: Insulin is synthesized as a precursor molecule known as pro-insulin. Pro-insulin consists of three main parts: the A-chain, the B-chain, and an additional segment called the C-peptide.

2. **Role of C-peptide**: The C-peptide is an extra peptide chain that is present in pro-insulin. It plays a crucial role during the maturation process of pro-insulin into insulin.

3. **Maturation Process**: The maturation of pro-insulin occurs in the Golgi apparatus of the cell. During this process, the C-peptide is excised (removed) from the pro-insulin molecule.

4. **Formation of Active Insulin**: After the removal of the C-peptide, the A-chain and B-chain of insulin are linked together by disulfide bridges (bonds). This results in the formation of the mature, biologically active insulin molecule.

5. **Conclusion**: Therefore, the C-peptide of human insulin is removed during the maturation of pro-insulin to insulin. This indicates that the correct answer to the question is that the C-peptide is excised during the processing of pro-insulin.

**Final Answer**: The C-peptide of human insulin is removed during maturation of pro-insulin to insulin.

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