Carbon Dioxide is Transported in the Blood Mostly as _______

Question

Carbon dioxide is transported in the blood mostly as _______.
A) carbon dioxide dissolved in the plasma
B) carboxyhemoglobin
C) bicarbonate ions
D) carbonic acid

Accepted Answer

Carbon dioxide in the blood is transported mostly as bicarbonate ions, which are formed from the reaction between carbon dioxide and water in the presence of carbonic anhydrase enzyme. This reaction occurs mostly in the red blood cells. The bicarbonate ions are then transported in the plasma to the lungs, where they are converted back to carbon dioxide for elimination. Small amounts of carbon dioxide also dissolve in the plasma and bind to hemoglobin as carbaminohemoglobin. However, these forms are minor compared to the bicarbonate ion form.