What form is the major component of carbon dioxide in blood?

What form is the major component of carbon dioxide in blood?

• A. Dissolved CO2
• B. Carbonate
• C. Bicarbonate Ion
• D. Carbonic Acid

Answer: (C)

At physiological pH, the majority of CO2 is transported in blood as bicarbonate ion. CO2 entering red blood cells is rapidly converted with water by carbonic anhydrase into carbonic acid, which immediately dissociates to bicarbonate and hydrogen ions. The bicarbonate then moves into plasma (with chloride ions moving in the opposite direction to maintain charge balance). This bicarbonate-dominant transport makes it the main form of CO2 in the blood. Dissolved CO2 is only a smaller fraction, carbonic acid is a fleeting intermediate, and carbonate ion is not a major species under normal blood pH.

At physiological pH, the majority of CO2 is transported in blood as bicarbonate ion. CO2 entering red blood cells is rapidly converted with water by carbonic anhydrase into carbonic acid, which immediately dissociates to bicarbonate and hydrogen ions. The bicarbonate then moves into plasma (with chloride ions moving in the opposite direction to maintain charge balance). This bicarbonate-dominant transport makes it the main form of CO2 in the blood. Dissolved CO2 is only a smaller fraction, carbonic acid is a fleeting intermediate, and carbonate ion is not a major species under normal blood pH.