Question

Approximately seventy percent of carbon-dioxide absorbed by the blood will be transported to the lungs.

• A. As bicarbonate ions
• B. In the form of dissolved gas molecules
• C. By binding to RBC
• D. As carbamino haemoglobin

Answer 1

The correct option is A As bicarbonate ions

About 70% of carbon dioxide is transported as sodium bicarbonate. As CO${}_2$ diffuses into the blood plasma, a large part of it combines with water to form carbonic acid in the presence of the enzyme carbonic anhydrase. Carbonic anhydrase is a zinc enzyme that speeds up the formation of carbonic acid. This carbonic acid dissociates into bicarbonate (HCO${}_3$${}^{–}$) and hydrogen ions (H${}^{+}$).