In red blood cells, carbon dioxide reacts with water to form what?

In red blood cells, carbon dioxide reacts with water to form what?

• A. Bicarbonate
• B. Carbonic acid
• C. Hydrochloric acid
• D. Sulfuric acid

Answer: (B)

The main concept is that carbon dioxide combines with water in red blood cells to form carbonic acid, a reaction that is catalyzed by the enzyme carbonic anhydrase. This carbonic acid (H2CO3) is formed in the hydration step and then rapidly dissociates into hydrogen ions and bicarbonate (HCO3−). The reason this is the best answer is that the question asks for the immediate product of the hydration reaction, which is carbonic acid, not bicarbonate. In practice, bicarbonate becomes the transported form in plasma after carbonic acid dissociates, and the reaction is reversible so it can produce CO2 again for exhalation in the lungs. The other acids listed (like hydrochloric or sulfuric acid) are not produced in this physiological process.

The main concept is that carbon dioxide combines with water in red blood cells to form carbonic acid, a reaction that is catalyzed by the enzyme carbonic anhydrase. This carbonic acid (H2CO3) is formed in the hydration step and then rapidly dissociates into hydrogen ions and bicarbonate (HCO3−). The reason this is the best answer is that the question asks for the immediate product of the hydration reaction, which is carbonic acid, not bicarbonate. In practice, bicarbonate becomes the transported form in plasma after carbonic acid dissociates, and the reaction is reversible so it can produce CO2 again for exhalation in the lungs. The other acids listed (like hydrochloric or sulfuric acid) are not produced in this physiological process.