In the structure of pro - insulin in humans disulphide bonds exist between

Options

A. between B peptide and C peptide
B. between A peptide and B peptide
C. between C peptide and A peptide
D. between A and C peptide as well as B and C peptide

Answer

To solve the question regarding the structure of pro-insulin in humans and the existence of disulfide bonds, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Pro-insulin Structure**: Pro-insulin is a precursor molecule to insulin, consisting of a single polypeptide chain made up of 86 amino acids. It contains three distinct regions: the A-peptide, B-peptide, and C-peptide.

2. **Identify the Peptides**: The pro-insulin molecule can be divided into:
- A-peptide
- B-peptide
- C-peptide

3. **Recognize the Role of Disulfide Bonds**: Disulfide bonds are covalent bonds that form between the sulfur atoms of cysteine residues in proteins. They play a crucial role in stabilizing the three-dimensional structure of proteins.

4. **Locate the Disulfide Bonds in Pro-insulin**: In pro-insulin, disulfide bonds specifically form between:
- A-peptide and B-peptide
- A-peptide and C-peptide
- B-peptide and C-peptide

5. **Conclusion**: The correct answer to the question is that disulfide bonds exist primarily between the A-peptide and B-peptide. However, it is important to note that there are also bonds involving the C-peptide.

### Final Answer:
Disulfide bonds exist between the A-peptide and B-peptide in the structure of pro-insulin in humans.