Read the paragraph given below and answer the question.
Insulin used for diabetes was earlier extracted from slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other type of reactions. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. In mammals, including human, insulin is synthesised as a pro-hormone.
Bonds which link 'A' and 'B' peptide chains of human insulin are
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Disulfide
Option (1) Peptide — Incorrect. Peptide bonds join the amino acids within each chain.
Option (2) Disulfide — Correct. Mature insulin has two short polypeptide chains, chain A and chain B, linked together by disulphide (S–S) bridges. Eli Lilly made the two chains separately in E. coli and joined them by these bridges.
Option (3) Covalent — Incorrect. Disulphide bonds are covalent, but the passage names them as disulphide bridges, the more exact answer.
Option (4) Hydrogen — Incorrect. Hydrogen bonds do not hold the two chains together.