Antibody molecule is made up of four peptide chain called as light and heavy chain are joined together by :
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Disulfide bond
An antibody has four polypeptide chains: two light and two heavy (H2L2). The chains are held together by disulfide bonds (S–S bridges between cysteine residues), shown in the NCERT figure of an antibody.
Option (1) Peptide bond — Incorrect. Peptide bonds join the amino acids within each chain, not one chain to another.
Option (2) Phosphodiester bond — Incorrect. Phosphodiester bonds join the nucleotides of DNA and RNA.
Option (3) Glycosidic bond — Incorrect. Glycosidic bonds join sugars in carbohydrates (and a base to a sugar in nucleotides).
Option (4) Disulfide bond — Correct. An antibody molecule has four peptide chains: two small light chains and two longer heavy chains (H2L2). The chains are held together by disulphide (S–S) bonds.