Percentage of cysteine in hemoglobin Steps:

• Hemoglobin consists of 2 α-globin (141 residues each) and 2 β-globin (146 residues each), totaling 574 amino acids.
• α-globin has 1 cysteine at position 104, so 2 cysteines from 2 α-chains.
• β-globin has cysteines at positions 93 and 112, so 4 cysteines from 2 β-chains.
• Total cysteines: 6; percentage = (6/574) × 100 ≈ 1.05%, which exceeds 1%.

Why A is correct:

• The calculation (6 cysteines / 574 total residues) × 100% = 1.05% confirms more than 1% are cysteine, based on hemoglobin's quaternary structure.

Why the others are wrong:

• B: Position 104 in 141-residue α-globin is central, not nearer the end; no info on reactivity.
• C: No evidence provided that replacing cysteine at 93 decreases oxygen affinity.
• D: Oxygen binding makes the region face outwards (hydrophilic exposure), but the statement reverses cause and effect; Bohr shift info is ambiguous.

Final answer: A