So basically, inside the cells of our tissue, different types of processes produce a bunch of carbon dioxide molecules. And because these molecules are non polar, they can easily diffuse across the membrane of the cells of the tissue and enter the extracellular matrix. And then they diffuse across the capillary walls found nearby our tissue cells. Now, once inside the blood plasma, the CO2, about 5% of that CO2 remains inside the blood plasma. But the rest essentially enters or diffuses across the membrane of the red blood cells. Now, once inside the red blood cells, what happens is a catalytic enzyme known as carbonic anhydrates, catalyzes the combination of gaseous, CO2 and liquid water to basically form an acid known as carbonic acid.