Final answer:
The majority of carbon dioxide in the blood is transported as bicarbonate. Carbon dioxide enters red blood cells and is converted into carbonic acid, which breaks down into bicarbonate and hydrogen ions. Bicarbonate is transported out of the red blood cells and eventually converted back into carbon dioxide in the lungs.
Step-by-step explanation:
The majority of carbon dioxide in the blood is transported as bicarbonate. When carbon dioxide enters red blood cells, it is converted into carbonic acid by an enzyme called carbonic anhydrase. This carbonic acid then breaks down into bicarbonate and hydrogen ions. Bicarbonate is transported out of the red blood cells and into the plasma in exchange for chloride ions, and it eventually reaches the lungs where it is converted back into carbon dioxide.