An insulin molecule in circulating in your bloodstream consists of:
a single chain of amino acids
four chains of amino acids linked together by disulfide bonds.
three chains of amino acids linked together by disulfide bonds
two chains of amino acids linked together by disulfide bonds
The Correct Answer and Explanation is :
The correct answer is: two chains of amino acids linked together by disulfide bonds.
Explanation:
Insulin is a peptide hormone crucial for regulating blood glucose levels. It is synthesized in the pancreas and consists of two polypeptide chains:
- The A-chain: Comprising 21 amino acids.
- The B-chain: Comprising 30 amino acids.
These two chains are linked together by two inter-chain disulfide bonds. Additionally, the A-chain contains an intra-chain disulfide bond, which helps stabilize its structure.
Key Details about Insulin Structure:
- Synthesis: Insulin is initially produced as a single polypeptide chain called preproinsulin. This precursor undergoes enzymatic cleavage to form proinsulin, which has three parts:
- An A-chain
- A B-chain
- A connecting peptide (C-peptide).
- Disulfide Bonds:
- Two inter-chain bonds between the A and B chains:
- Between cysteine residues on the A-chain (position 7) and B-chain (position 7).
- Between cysteine residues on the A-chain (position 20) and B-chain (position 19).
- One intra-chain bond within the A-chain, between its cysteine residues at positions 6 and 11.
- Two inter-chain bonds between the A and B chains:
- Biological Function: This three-dimensional structure is critical for insulin’s biological activity. The disulfide bonds stabilize the molecule and ensure it retains its active configuration, which is essential for binding to insulin receptors on target cells.
Summary:
Insulin in the bloodstream is a mature molecule consisting of two polypeptide chains (A and B) connected by disulfide bonds. This structure is essential for its stability and function in regulating glucose metabolism.