The largest proportion of the carbon dioxide delivered from peripheral tissues to the lungs is carried in the blood:

a. in combination with hemoglobin in red blood cells

b. dissolved in the fluid portion of the blood

c. as plasma bicarbonate

d. in combination with plasma proteins

Answer: The correct answer would be option a.

Explanation:

The hemoglobin in red blood cell has a tendency to bind to oxygen as well carbon dioxide in a reversible manner. It depends upon the partial pressure of the gas.

For example, at tissue site, the concentration of carbon dioxide is higher than oxygen due to which the affinity of hemoglobin increases for carbon dioxide.

In hemoglobin, carbon dioxide reacts with water to form bicarbonate ions and hydrogen ions.

At alveolar site, these ions again convert into carbon dioxide and excrete out of the blood as a part of exhale air.