Now, what about the carbon dioxide effect? So carbon dioxide is produced inside the exercising cells of our body. So if our muscles are contracting, we're producing more CO2 molecules. Now, the thing about CO2 molecules is they're non polar molecules and they can easily move across the cell membrane of the tissue. Cells move into our blood system and then move into the red blood cells because they don't have a charge and they can easily pass across the cell membrane. Along with that, we also have special protein transporters in the cell membrane that allow the carbon dioxide to basically be brought into the red blood cell.