Question

Which one of the following is an example of buffer system in blood?

• A. Haemoglobin and oxyhaemoglobin
• B. Oxygen and carbon dioxide
• C. Albumin and globulin
• D. Sodium bicarbonate and carbonic acid

Answer 1

Answer: (D)

Sodium bicarbonate and carbonic acid

Carbonic acid (H${}_2$CO${}_3$) is a weak acid and is therefore in equilibrium with bicarbonate (HCO${}_3$${}^{-}$) in solution. When significant amounts of both carbonic acid and bicarbonate are present, a buffer is formed. This buffer system can be written as H${}_2$CO${}_3$${}^{+}$ H${}_2$O --> H${}_3$O${}^{+}$ + HCO${}_3$${}^{-}$. Under normal circumstances there is much more bicarbonate present than carbonic acid (20 : 1). As normal metabolism produces more acids than bases, the blood with its high base concentration, is able to neutralize the metabolic acids produced.