Identify the wrong statement with reference to the structure of human insulin

Options

A. Insulin is synthesised as a pre-hormone which contains an extra stretch called C-peptide
B. A and B chains are combined by disulphide bonds to form humulin
C. Human insulin is made up of 51 amino acids arranged in two polypetide chains
D. In these, chain A is made up of 30 amino acids and chain B is made up of 21 amino acids.

Answer

### Step-by-Step Text Solution

1. **Understanding Human Insulin Structure**: Human insulin, also known as Humulin, is a peptide hormone composed of two polypeptide chains, referred to as the A chain and the B chain.

2. **Composition of Insulin**: The A chain consists of 30 amino acids, while the B chain consists of 21 amino acids. Together, they form a total of 51 amino acids in the insulin molecule.

3. **Prehormone and C-Peptide**: Insulin is initially synthesized as a prehormone called proinsulin, which contains an additional segment known as the C-peptide. This C-peptide connects the A and B chains in the inactive form of insulin.

4. **Activation of Insulin**: To convert proinsulin into active insulin, the C-peptide must be removed. This process is essential for the activation of insulin, allowing it to function properly in the body.

5. **Recombinant DNA Technology**: In the production of human insulin using recombinant DNA technology, the A and B chains are synthesized separately. These chains do not include the C-peptide, meaning they are produced in their active form.

6. **Identifying the Wrong Statement**: Based on the information provided, the wrong statement regarding the structure of human insulin is that it contains the C-peptide when synthesized in the active form. In reality, the active form of insulin (Humulin) does not have the C-peptide.

### Conclusion
The wrong statement is that human insulin (Humulin) is synthesized with the C-peptide present in its active form. Instead, it is synthesized without the C-peptide.

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