Human insulin has 51 amino acids in two chains. Mark the correct statement.

Options

A. (a) A chain with 21 and B chain with 30 amino acids.
B. (b) A chain with 20 and B chain with 31 amino acids.
C. (c) A chain has 31 and B chain has 20 amino acids.
D. (d) A chain has 30 and B chain has 21 amino acids.

Answer

To solve the question regarding the structure of human insulin and to identify the correct statement about its amino acid composition, follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Insulin**:
- Human insulin is composed of two chains known as the A chain and the B chain.

2. **Identify the Number of Amino Acids**:
- The A chain consists of 21 amino acids.
- The B chain consists of 30 amino acids.

3. **Recognize the Role of C Peptide**:
- Insulin is initially synthesized as proinsulin, which includes an additional segment called the C peptide.
- The C peptide is removed to form the active insulin, which consists only of the A and B chains.

4. **Determine the Correct Statement**:
- Given the options, we need to identify which statement correctly describes the number of amino acids in the A and B chains.
- The correct statement is: "A chain with 21 amino acids and B chain with 30 amino acids."

5. **Eliminate Incorrect Options**:
- Review the other options provided:
- A chain with 20 and B with 31 (incorrect).
- A chain with 31 and B with 20 (incorrect).
- Any other combination that does not match the correct counts (incorrect).
- Confirm that the only accurate statement is the one indicating 21 amino acids in the A chain and 30 in the B chain.

### Final Answer:
The correct statement is: **A chain with 21 amino acids and B chain with 30 amino acids.**

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