So remember, we have oxygen molecules moving from the red blood cells into this area, then into this area, and eventually that makes their way into the cells of the exercising tissue. Now, what about the bicarbonate ions? Well, bicarbonate ions are simply another form of the carbon dioxide. But the major difference between the carbon dioxide and the bicarbonate is the bicarbonate contains a full negative charge. And that makes this molecule polar. And what that means is if the molecule moves into the blood plasma, it will have no problem dissolving in the polar blood plasma.