And let's suppose the tissue is exercising. So it has a high rate of metabolism. And what that means is it produces a high concentration of carbon dioxide molecules as a wasteful. Byproduct now, these carbon dioxide molecules diffuse across the cell membrane into the extracellular matrix, and they travel into the blood plasma of the nearby capillary. So this is the wall of our capillary. Now, when the CO2 molecules enter the blood plasma then travel into the red blood cell.