Proinsulin synthesized in human is composed of

Options

A. A, B and C peptides
B. peptide only
C. A & B peptides only.
D. B and C peptides

Answer

To answer the question regarding the composition of proinsulin synthesized in humans, we can break down the information step by step:

### Step-by-Step Solution:

1. **Understanding Insulin Structure**:
- Insulin is a hormone that regulates glucose levels in the blood and is composed of two main polypeptide chains known as the A chain and B chain.

2. **Proinsulin Definition**:
- Proinsulin is the precursor to insulin. It is an immature form of insulin that is synthesized in the pancreas.

3. **Composition of Proinsulin**:
- Proinsulin consists of three components:
- **A Chain**: One of the two chains that will eventually form mature insulin.
- **B Chain**: The second chain that pairs with the A chain in mature insulin.
- **C Peptide**: An additional segment that is present in proinsulin but is removed during the maturation process to form active insulin.

4. **Maturation Process**:
- During the maturation of proinsulin into insulin, the C peptide is cleaved off, resulting in the formation of the active insulin molecule, which consists only of the A and B chains.

5. **Final Answer**:
- Therefore, proinsulin synthesized in humans is composed of A chain, B chain, and C peptide.

### Conclusion:
The correct answer is that proinsulin is composed of A, B, and C peptides.

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