Now, as soon as the binding takes place, when the two three BPG binds into that space inside the adult hemoglobin, it creates a change in the structure of the adult hemoglobin. And what that does is it decreases the adult hemoglobin's ability to actually bind to oxygen. It lowers its affinity for oxygen. So when the binding takes place, that adult hemoglobin is much less likely to actually bind oxygen and carry oxygen from point A to point B. Now, what about the fetal hemoglobin? Well, just like the delt hemoglobin, the fetal hemoglobin also consists of four subunits.