Biology – Transport of oxygen and carbon dioxide | e-Consult

Carbonic anhydrase is an enzyme found in high concentrations within red blood cells. Its primary role is to catalyze the reversible reaction between carbon dioxide (CO2) and water (H2O) to form carbonic acid (H2CO3). This is a crucial step in the transport of CO2 because it allows for the conversion of CO2 into bicarbonate ions (HCO3-), which is the major form of CO2 transport in the blood.

The reaction equation is as follows:

In the tissues, where CO2 concentration is high, the enzyme facilitates the formation of carbonic acid, which then dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-). The bicarbonate ions are transported out of the red blood cells into the plasma, while the hydrogen ions bind to haemoglobin, contributing to the Bohr effect (which promotes CO2 release in the tissues).

In the lungs, the process is reversed. The enzyme catalyzes the breakdown of bicarbonate ions back into CO2 and water, which then diffuses into the alveoli to be exhaled.