Myoglobin vs hemoglobin binding Either hemoglobin or myoglobin, both serve as oxygen-binding macromolecules . , “tense” state) of hemoglobin has a low affinity for O 2 and is favored by a lack of bound O 2. Thus, hemoglobin has four separate heme groups that can bind a molecule of O 2 . 0 pO 2 (kPa) P 50 1 Feb 17, 2017 ยท Sketch binding curves for the oxygenation of myoglobin and hemoglobin. The main difference between hemoglobin and myoglobin is The binding of oxygen to hemoglobin can be plotted as a function of the partial pressure of oxygen in the blood (x-axis) versus the relative Hb-oxygen saturation (y-axis). It's also 99%, which is really close to 98%. The transition between the T and the R state of hemoglobin is mediated by the chemistry of the heme complex. So, really, they're binding in the lungs. In the case of myoglobin, the KD is 2-3 torr. They are accountable for the red color in their respective areas.