In mature insulin chain-A and chain-B are linked together by which bond?

Answer

**Step-by-Step Solution:**

1. **Understanding Insulin Structure**: Insulin is a protein hormone composed of two peptide chains known as chain A and chain B.

2. **Identifying the Chains**: Chain A consists of 21 amino acids, while chain B consists of 30 amino acids.

3. **Linkage Between Chains**: The two chains (A and B) of insulin are linked together by specific types of bonds.

4. **Types of Bonds**: The primary bonds that link chain A and chain B are disulfide bonds.

5. **Counting the Bonds**: There are two disulfide bonds that connect chain A and chain B. Additionally, there is another disulfide bond that is formed within the A chain itself.

6. **Conclusion**: Therefore, the correct answer to the question is that chain A and chain B of mature insulin are linked together by disulfide bonds.

**Final Answer**: Chain A and chain B of mature insulin are linked together by disulfide bonds.

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