So it stores the oxygen in the muscle cells of our body because it only releases it when the concentration drops to very low value. On the other hand, because the hemoglobin consists of these four individual polypeptide chains, these polypeptide chains, the heme groups can interact with one another and they can basically induce the release or the binding of the oxygen. And so this means if it makes it a perfect molecule to act as a carrier of oxygen inside our blood system, so that's exactly why hemoglobin is used by our body to basically take that oxygen in the lungs and bring it to the tissues of our body. So we see that hemoglobin's cooperative behavior makes it a great oxygen carrier. It can readily bind that two in the lungs and has no problem releasing that oxygen inside the tissues of our body. And we'll discuss in much more detail what the physiological consequence is of hemoglobin and myoglobin.