Question

The diagram given below represents the schematic structure of proinsulin, which undergoes certain modifications before it becomes a fully functional insulin.

Study the diagram carefully and answer the questions that follow:

1. State the change the proinsulin undergoes to become fully functional.
2. Name the modern scientific technique used for the production of human insulin.
3. How are the two polypeptide chains of the fully functional insulin held together?

Answer 1

1. Proinsulin undergoes a chemical change in which the C-peptide is cleaved and eliminated before becoming completely functional as mature insulin. The C-chain breaks to generate an active insulin molecule.
2. Recombinant DNA (rDNA) technology is used to produce human insulin.
3. Disulfide bonds connect the two polypeptide chains, the A chain (21 amino acids) and the B chain (30 amino acids), to form the fully functioning insulin molecule. These chains are linked by two disulfide bonds, while the A chain contains an additional internal disulfide bond. These connections are critical to insulin's structure and activity.