Question

as the partial pressure of oxygen increases, which of the following is true?
a.) the number of heme units with oxygen bound decreases, but the oxygen saturation of the blood increases.
b.) the number of heme units with oxygen bound increases, but the oxygen saturation of the blood decreases.
c.) the number of heme units with oxygen bound and the oxygen saturation of the blood increase.
d.) the number of heme units with oxygen bound and the oxygen saturation of the blood decrease.

Explanation:

According to the principles of oxygen - hemoglobin binding, when the partial pressure of oxygen ($pO_2$) increases, more oxygen molecules bind to the heme units of hemoglobin. The oxygen saturation of the blood, which is the percentage of hemoglobin that is bound to oxygen, also increases.

Answer:

C. The number of heme units with oxygen bound and the oxygen saturation of the blood increase.