Carbonic anhydrase catalyzes CO2 hydration to carbonic acid

Steps:

• Identify carbonic anhydrase's role in converting CO2 and H2O to H2CO3 rapidly.
• Review choices for direct match to CO2 + H2O → H2CO3 reaction.
• Eliminate options involving hemoglobin or acid dissociation.
• Confirm D as the precise association reaction.

Why D is correct:

• Carbonic anhydrase catalyzes CO2 + H2O ⇌ H2CO3, the association of carbon dioxide and water, accelerating it by 10,000-fold.

Why the others are wrong:

• A: Dissociation of H2CO3 to H+ and HCO3- occurs spontaneously, not directly by the enzyme.
• B: Carbaminohemoglobin forms via direct binding of CO2 to hemoglobin, without enzymatic catalysis.
• C: HCO3- and H+ form from H2CO3 breakdown, which the enzyme indirectly facilitates but does not directly catalyze.

Final answer: D