Well, it's basically the Cooperativity, the fact that hemoglobin is cooperative. It consists of four individual polypeptide subunits and these units interact with one another that creates this S shape. But because myoglobin does not have those four polypeptide subunits, it only contains one. It contains the following curve. Now, the next question is what exactly is the physiological significance of these two curves? And how do these curves actually correspond to the function of these two different proteins?