Now, the majority of the carbon dioxide in the red blood cells is transformed into bicarbonate ions and hydrogen ions. So by increasing the amount of CO2 inside the red blood cell, we also in turn increase the amount of hydrogen ions inside our red blood cells. And because hydrogen ions, the concentration of hydrogen ions, determines the PH of our blood plasma, and what that means is a higher concentration of hydrogen ions means a more acidic environment and so a lower PH. Now, what exactly is the effect that hydrogen has on hemoglobin? Well, it turns out that hydrogen ions can actually bind onto special allosteric sites found on our hemoglobin. And by binding to hemoglobin, the hydrogen ions effectively decrease the affinity of hemoglobin for oxygen.