Carbonic anhydrase catalyzes CO2 hydration to bicarbonate

Steps:

• Carbonic anhydrase (CA) accelerates CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-, essential for CO2 transport and pH regulation.
• Identify reactions dependent on rapid bicarbonate formation: typically those in red blood cells, renal tubules, and gastric mucosa.
• Reaction 1 likely independent (e.g., direct CO2 diffusion or unrelated enzyme pathway).
• Reactions 2 and 3 require CA for efficient catalysis, so inhibition slows them.

Why D is correct:

• CA inhibition specifically targets bicarbonate-dependent reactions 2 and 3, per the enzyme's role in the reversible hydration reaction.

Why the others are wrong:

• A includes reaction 1, which does not rely on CA.
• B omits reaction 3, a CA-dependent process.
• C omits reaction 2, also CA-dependent.

Final answer: D