A right shift on the oxygen affinity curve is associated with which changes in pH, temperature, and PCO2?

A right shift on the oxygen affinity curve is associated with which changes in pH, temperature, and PCO2?

• A. Increase pH; Decrease temperature; Decrease PCO2
• B. Decrease pH; Increase temperature; Increase PCO2
• C. Increase pH; Increase temperature; Increase PCO2
• D. Decrease pH; Decrease temperature; Decrease PCO2

Answer: (B)

A right shift on the oxygen-hemoglobin dissociation curve means hemoglobin holds onto oxygen less tightly and releases it more readily to tissues. This occurs when the tissue environment promotes unloading: lower pH (more acidic), higher temperature, and higher CO2 levels. The increase in CO2 and H+ (from CO2 hydration and the Bohr effect) together with heat all reduce Hb’s affinity for O2, shifting the curve to the right and increasing the P50 (the PO2 at which Hb is 50% saturated). Therefore, the combination of decreased pH, increased temperature, and increased PCO2 best fits a rightward shift. The other options would tend to increase Hb's affinity (left shift) by raising pH, lowering temperature, or lowering CO2.

A right shift on the oxygen-hemoglobin dissociation curve means hemoglobin holds onto oxygen less tightly and releases it more readily to tissues. This occurs when the tissue environment promotes unloading: lower pH (more acidic), higher temperature, and higher CO2 levels. The increase in CO2 and H+ (from CO2 hydration and the Bohr effect) together with heat all reduce Hb’s affinity for O2, shifting the curve to the right and increasing the P50 (the PO2 at which Hb is 50% saturated). Therefore, the combination of decreased pH, increased temperature, and increased PCO2 best fits a rightward shift. The other options would tend to increase Hb's affinity (left shift) by raising pH, lowering temperature, or lowering CO2.