[Campbell Biology P.997] According to Figure 42.31a, approximately what percentage of oxygen... | Practice Question

According to Figure 42.31a, approximately what percentage of oxygen is unloaded from hemoglobin when blood moves from resting tissues PO2 40 mm Hg to metabolically very active tissues during exercise PO2 20 mm Hg ?

  • A: 10%
  • B: 30%
  • C: 50%
  • D: 70%

Explanation

Figure 42.31a shows that at a PO2 of 40 mm Hg resting tissues , hemoglobin is about 70% saturated with O2. During exercise, in metabolically very active tissues, the PO2 drops significantly, for example, to about 20 mm Hg. At this PO2, the curve indicates an O2 saturation of roughly 40%. Therefore, the additional oxygen unloaded is approximately 70% - 40% = 30% of the total O2 capacity.