Sulthiame Inhibits CO2 Hydration in RBCs

Steps:

• High-rate muscle respiration produces excess CO2, which diffuses into red blood cells (RBCs).
• Inside RBCs, carbonic anhydrase catalyzes CO2 + H2O → H2CO3 (carbonic acid), which dissociates to HCO3- and H+.
• Sulthiame inhibits carbonic anhydrase, slowing the hydration of CO2 to H2CO3.
• This directly reduces the rate of carbonic acid formation, impairing CO2 transport.

Why A is correct:

• Carbonic anhydrase accelerates CO2 + H2O ⇌ H2CO3 by ~10,000-fold; inhibition decreases this catalyzed rate per enzyme kinetics.

Why the others are wrong:

• B: Slower H+ production from H2CO3 reduces acidification, so pH increases, not decreases.
• C: Chloride shift relies on HCO3- efflux after carbonic acid formation; inhibition slows HCO3- production, decreasing the shift.
• D: Oxyhemoglobin dissociation increases with lower pH via Bohr effect; here, reduced acidification hinders dissociation.

Final answer: A