So remember, the carbonic anhydrase enzyme is only found within our red blood cell. It is not found inside the blood plasma. And that's why this anion must first cross the membrane and enter the red blood cell before we can actually form our carbon dioxide. Now, once we form the carbon dioxide, because it is nonpolar, it can easily diffuse across the membrane of the red blood cell, then across our wall of the capillary, and finally enter the alveolar space, where we exhale. And we basically expel that carbon dioxide to the outside environment. So we see that the chloride shift takes place inside the red blood cells and it takes place not only in the tissues but also in the lungs.