The polypeptide chains A and B in Insulin are linked together by:

The correct answer is Option (3) → Disulphide bonds

Option (1) Covalent bonds — Incorrect. Disulphide bonds are covalent, but disulphide is the specific answer.

Option (3) Disulphide bonds — Correct. Of the options, only disulphide bonds is the link NCERT names between chains A and B.

Note: A similar question was also asked in CUET (UG) 2026 on 30-05-2026 (Slot 2) and on 25-05-2026 (Slot 1).

NCERT Extract:
Genetically Engineered Insulin – “… Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges (Figure 10.3).”

Figure 10.3 Maturation of pro-insulin into insulin (simplified)