Biology Immunity PMDC Conceptual Practice
PMDC Verified Question 44 of 99
In a classic \(\text{IgG}\) immunoglobulin, the two heavy chains and two light chains are covalently bonded by:
A
Disulphide bridges
B
Peptide bonds
C
Hydrogen bonds
D
Ionic bonds
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Disulphide bridges
Concept: Chemical bonding in antibody quaternary structure.

Solution: Covalent disulphide bridges (\(\text{-S-S-}\)) between cysteine residues link the heavy chains to each other and bind each light chain to a heavy chain.

Why other options are incorrect:
  • Option B: Peptide bonds form the primary sequence within individual chains, but disulphide bridges covalently link separate polypeptide chains together.

  • Option C & Option D: Non-covalent forces assist folding, but covalent disulphide bonds hold the quaternary assembly together.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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