Bicarbonate-Carbonic Acid Buffer

The carbonic acid–bicarbonate buffer system works on the principle of bicarbonate ions acting as a weak base and carbonic acid functioning as a weak acid.

Bicarbonate ions effectively neutralize the excess hydrogen ions in acidic conditions by accepting them to form carbonic acid.

The newly formed carbonic acid, catalyzed by carbonic anhydrase, dissociates into carbon dioxide and water. The carbon dioxide formed is exhaled from the lungs.

If there is a decrease in the plasma concentration of hydrogen ions, carbonic acid compensates by dissociating and releasing more hydrogen ions.

The effectiveness of this buffer system depends on the concentrations of buffering substances.

When the system becomes overwhelmed by excess acid and exhausts all available bicarbonate ions, also called the alkaline reserve, the buffer system loses its effectiveness, resulting in changes in the blood pH.

However, this is rare because body fluids have abundant bicarbonate ions, which the kidneys can reabsorb when needed.

Because a steady supply of carbon dioxide is needed to form carbonic acid, this buffer system fails to protect against pH changes in cases of respiratory problems.