Now, once the CO2 is inside the red blood cell, it reacts with water. And with the help of a special enzyme known as carbonic and hydrase, we transform CO2 and water into carbonic acid. And then, because carbonic acid is a relatively good acid, it will dissociate into H plus ions and into bicarbonate ions. The bicarbonate ion will have a negative charge. The h plus ion will have a positive charge. Now, notice one important thing.