Question

Which reaction involving CO2 predominates within erythrocytes in the pulmonary capillaries of the lung?

A. HCO3 ^- combines with H^+ to form H2CO3, which dissociates into CO2 and H2O
B. HCO3^- dissociates into H+, CO and O2
C. CO2 combines with H+ to form HCO2
D. CO2 combines with water to form bicarbonate ion and carbonic acid.

Answer 1

At the pulmonary capillaries, HCO3^- dissociates into H+, CO2, and O2 within erythrocytes.

Step-by-step explanation:

At the pulmonary capillaries, the reaction that predominates within erythrocytes is the following:

B. HCO3- dissociates into H+, CO2, and O2

Inside erythrocytes, carbon dioxide combines with water to form carbonic acid (H2CO3), which dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+). This reaction is catalyzed by an enzyme called carbonic anhydrase. The bicarbonate ions can then re-enter the plasma, while the hydrogen ions combine with hemoglobin. In the pulmonary capillaries, bicarbonate ions re-enter the erythrocytes in exchange for chloride ions, and carbonic acid is converted back into carbon dioxide and water.