And that's because the entire purpose of the tissue is to take the CO2 and bring it into the red blood cells. But the entire purpose of the lungs is to take the CO2 from the red blood cell and bring into the space of our alveoli, which ultimately expels that CO2 during the process of exhalation. So let's see what takes place. So, the bicarbonate ion enters the blood plasma, and then it travels with the blood plasma all the way to the pulmonary capillaries. And once we find it in the pulmonary capillaries, what happens is the opposite process takes place. Now, in order to maintain electrical neutrality, when a single bicarbonate ion enters our red blood cell, a single chloride ion must leave that red blood cell so that we have a net charge of zero that essentially travels across the red blood cells.