Question

Although much carbon dioxide is carried in blood, yet blood does not become acidic because

• A. $C{O}_2$ is continuously diffused through the tissues and is not allowed to accumulate
• B. $C{O}_2$ combines with water to form $H_{2}C{O}_3$, which is neutralised by $N{a}_{2}C{O}_3$
• C. In $C{O}_2$ transport, blood buffers play an important role
• D. $C{O}_2$ is absorbed by leucocytes

Answer 1

The correct option is C In $C{O}_2$ transport, blood buffers play an important role

Although much carbon dioxide is carried in the blood, yet blood does not become acidic because of the role of blood buffers. The carbonic acid or carbonate is a weak acid and is, therefore, in equilibrium with bicarbonate $\left(HC{O}_3^{-}\right)$ ions in solution. The significant amount of both carbonic acid and bicarbonate make a buffer in the blood which maintains the pH at a constant level.
Carbon dioxide enters RBC and reacts with water to form carbonic acid. Carbonic acid dissociates to form bicarbonate and hydrogen ions. Some bicarbonate ions are transported in erythrocytes while some diffuse into the blood plasma. Exit of bicarbonate ions change the ionic balance between the plasma and erythrocytes. To restore this balance chloride ions diffuse from plasma into erythrocytes. Due to this the pH of blood is maintained.