Now, once inside the red blood cell, what we have to do is we have to convert the carbon dioxide, a non polar molecule, into a polar form, namely the bicarbonate. And that's because we want to be able to dissolve the carbon dioxide in the blood. So the majority of the carbon dioxide in the red blood cell will follow this reaction pathway. So a special enzyme we call carbonic anhydrase will combine carbon dioxide and water to form the carbonic acid molecule. And then the carbonic acid being a good acid, it will dissociate into H plus ions and the bicarbonate ions. And this is where the halding effect takes place.