The question is why? Why does this take place, and what effect does it have on our tissues? Well, basically, once carbon monoxide actually binds onto one of the heme groups of hemoglobin, it decreases the amount of oxygen that the hemoglobin can actually bind. For example, if a given hemoglobin molecule is bound to two carbon monoxide, that means only two oxygen can actually bind onto the hemoglobin versus the four oxygen in the normal case. So what this does is it decreases the oxygen carrying capacity of the hemoglobin inside our blood plasma, and that's why we have the drop in this curve. And that means, because we have a decrease in oxygen carrying capacity, once again, less oxygen will be ultimately delivered to the tissues of our body.