Question

How does H2CO3 resist a rise in pH?

Answer 1

H2CO3 acts as a buffer in the blood and maintains the pH of the blood. Buffers are very important as they exist as mixture of conjugate acid-base pair and maintains the pH whenever a little acid or base is added to it. In blood, the buffer system that is responsible to maintain pH are carbonic acid (H2CO3) and bicarbonate ion (HCO3-).

Entry of acidic substance in the bloodstream causes the bicarbonate ions to neutralize the hydronium (H3O+) forming carbonic acid and water.

On the contrary, when a basic substance enters the bloodstream, the carbonic acid reacts with the hydroxide ions (OH-). This now produces bicarbonate ions and water.