Question

1. Consider the allosteric regulation of hemoglobin's binding affinity for oxygen. For the various conditions listed in the question below, determine the affect on hemoglobin's binding affinity and provide a brief explanation for your reasoning. 1) What affect (if any) would a change in blood pH from 7.4 to 7.2 have on hemoglobin's binding affinity for oxygen? Briefly Explain. 2) What affect (if any) would a decrease in BPG levels from 8 mM (physiological adaptation at high altitudes) to 5 mM (physiological level at normal altitudes) have on hemoglobin's binding affinity for oxygen? Briefly Explain.

Answer 1

The oxygen affinity of hemoglobin decreases as pH decreases from the value of 7.4 found in the lungs. Thus, as hemoglobin moves into a region of low pH, its tendency to release oxygen increases. Lowering the pH from 7.4 (red curve) to 7.2 (blue curve) results in the release of O₂ from oxyhemoglobin. Raising the CO₂ partial pressure from 0 to 40 torr (purple curve) also favors the release of O₂ from oxyhemoglobin.

High altitude environments pose a number of unique physiological challenges to animal life. In addition to the characteristically cold temperatures, high altitude environments are also characterized by lower partial pressures of oxygen () relative to low altitude environments at similar latitudes. Since the reduced of inspired air will typically result in a concomitant reduction in the O₂ saturation of arterial blood, a suite of compensatory physiological adjustments may be required to ensure an adequate supply of O₂ to the cells of aerobically metabolizing tissues.