CO2 Conversion to Bicarbonate in Red Blood Cells

Steps:

• CO2 from active cells diffuses into red blood cells (RBCs).
• Inside RBCs, carbonic anhydrase enzyme catalyzes CO2 + H2O → H2CO3, which dissociates into H+ and HCO3-.
• This reaction increases H+ (hydrogen ions) and HCO3- (bicarbonate ions) concentrations.
• Carbonic anhydrase concentration remains unchanged as it's an enzyme, not a reactant.

Why D is correct:

• The bicarbonate buffer system formula (CO2 + H2O ⇌ H+ + HCO3-) directly produces more H+ and HCO3- without altering enzyme levels.

Why the others are wrong:

• A: Carbonic anhydrase does not decrease; H+ and HCO3- both increase.
• B: Carbonic anhydrase concentration does not increase; it's catalytic.
• C: H+ increases, not decreases, due to acid dissociation.

Final answer: D