Antibody Structure Fundamentals

Steps:

• Statement 1 is correct: Antibodies rely on hydrogen bonds for secondary/tertiary folding and disulfide bonds for stabilizing chains.
• Statement 2 is correct: As proteins, antibodies exhibit tertiary structure in individual chains and quaternary structure from four polypeptide subunits (two heavy, two light).
• Statement 3 is incorrect: The four polypeptides form two Fab regions, providing only two antigen-binding sites, not four.
• Overall, only statements 1 and 2 hold true, matching option B.

Why B is correct:

• Antibodies are Y-shaped immunoglobulins with quaternary structure from multiple subunits, as defined in protein biochemistry, supporting bonds in 1 and structures in 2.

Why the others are wrong:

• A: Includes incorrect statement 3 about four binding sites.
• C: Excludes correct statement 2 on protein structures.
• D: Excludes correct statement 1 on bonding.

Final answer: B