Now, why does this actually take place? Well, let's take a look at our tissue partial pressure of 40 mercury. So if we draw a vertical line and we find the corresponding Y coordinates, the Y points for the blue curve, when we don't have any two three BPG present in the red blood cells found inside the capillaries, we see that we have a percent equaling to about 70% saturation of hemoglobin. But at the same exact partial pressure for our curve that contains the two three BPG, we have a value of about 60% saturation of hemoglobin. And the fact that we have less saturation of hemoglobin in our red blood cells that contain the two three BPG. That basically means more of these hemoglobin molecules are not actually bound to the oxygen.