So this is how gas exchange actually takes place. Now, the question we want to ask in this lecture is what exactly makes the placenta effective and efficient in actually exchanging that oxygen and what allows it to exchange that oxygen, carbon dioxide, in the right direction. So remember, we want the placenta not only to exchange the gases quickly and efficiently, but we also want to exchange the gasses in the right direction. So we must make sure that oxygen always travels into that fetus and carbon dioxide is always removed from that fetus and moves into the blood capillaries and the blood system of the mother. So there are three factors that affect the efficiency of that placenta, and one of them is the type of hemoglobin molecule that is found inside the blood of that fetus. So recall that oxygen is actually a nonpolar molecule.