Structural Biochemistry/Protein function/Myoglobin's Oxygen Binding Curve
The oxygen binding curve for Myoglobin forms an asymptotic shape, which shows a simple graph that rises sharply then levels off as it reaches the maximum saturation. The half-saturation, the point at which half of the myoglobin is binded to oxygen, is reached at 2 torr which is relatively low compared to 26 torr for hemoglobin.
Myoglobin has a strong affinity for oxygen when it is in the lungs, and where the pressure is around 100 torr. When it reaches the tissues, where it's around 20 torr, the affinity for oxygen is still quite high. This makes myoglobin less efficient of an oxygen transporter than hemoglobin, which loses it's affinity for oxygen as the pressure goes down and releases the oxygen into the tissues. Myoglobin's strong affinity for oxygen means that it keeps the oxygen binded to itself instead of releasing it into the tissues.