The extent of O2 binding is high for myoglobin and low for hemoglobin at pH 7.2 and 10 Torr oxygen partial pressure.

Myoglobin and Hemoglobin:
Before discussing the extent of O2 binding for myoglobin and hemoglobin, let's understand their basic structure and function:

- Myoglobin: Myoglobin is a single polypeptide chain that consists of 153 amino acids. It has a heme group, which is responsible for binding to O2. Myoglobin is mainly found in muscle tissues and acts as an O2 reservoir, facilitating O2 diffusion within the muscle cells.

- Hemoglobin: Hemoglobin is a tetramer composed of four polypeptide chains - two α chains and two β chains. Each chain has a heme group. Hemoglobin is found in red blood cells and is responsible for transporting O2 from the lungs to the body tissues.

Extent of O2 Binding:
The extent of O2 binding is determined by the affinity of the heme group for O2, which is influenced by factors like pH and partial pressure of oxygen. In this case, at pH 7.2 and 10 Torr oxygen partial pressure:

1. Myoglobin:
- At a pH of 7.2, myoglobin exhibits a high affinity for O2. This is because myoglobin has a lower affinity for protons (H+) compared to hemoglobin. At pH 7.2, the concentration of protons is relatively low, allowing myoglobin to have a higher affinity for O2.
- At a partial pressure of 10 Torr, myoglobin also has a high affinity for O2. Myoglobin has a higher affinity for O2 compared to hemoglobin at low oxygen partial pressures. This allows myoglobin to effectively bind O2 even at low oxygen concentrations.

2. Hemoglobin:
- At a pH of 7.2, hemoglobin exhibits a lower affinity for O2 compared to myoglobin. Hemoglobin has a higher affinity for protons (H+) compared to myoglobin. At a pH of 7.2, the concentration of protons is relatively high, leading to a decrease in the affinity of hemoglobin for O2.
- At a partial pressure of 10 Torr, hemoglobin has a lower affinity for O2 compared to myoglobin. Hemoglobin has a higher affinity for O2 at high oxygen partial pressures, such as those found in the lungs. At low oxygen partial pressures, hemoglobin releases O2 more readily, allowing for efficient delivery to the tissues.

Conclusion:
Based on the above factors, the extent of O2 binding is high for myoglobin and low for hemoglobin at pH 7.2 and 10 Torr oxygen partial pressure.