Which factor is listed as causing a rightward shift of the oxyhemoglobin curve by increasing metabolic activity?

Which factor is listed as causing a rightward shift of the oxyhemoglobin curve by increasing metabolic activity?

• A. Increased CO2
• B. Increased pH
• C. Decreased temperature
• D. Decreased 2,3-BPG

Answer: (A)

When metabolism is high, tissues produce more CO2, which lowers pH and promotes O2 release from hemoglobin. The rightward shift of the oxyhemoglobin curve means hemoglobin binds O2 less tightly, making it easier to unload O2 where it’s needed. Increased CO2 directly contributes to this effect (the Bohr and carbamino effects), so more CO2 pushes the curve to the right. In contrast, higher pH (alkalosis) would increase Hb’s affinity for O2 and shift the curve left, lower temperature would also shift left, and less 2,3-BPG would reduce the rightward shift. Thus increased CO2 best explains the rightward shift with increased metabolic activity.

When metabolism is high, tissues produce more CO2, which lowers pH and promotes O2 release from hemoglobin. The rightward shift of the oxyhemoglobin curve means hemoglobin binds O2 less tightly, making it easier to unload O2 where it’s needed. Increased CO2 directly contributes to this effect (the Bohr and carbamino effects), so more CO2 pushes the curve to the right. In contrast, higher pH (alkalosis) would increase Hb’s affinity for O2 and shift the curve left, lower temperature would also shift left, and less 2,3-BPG would reduce the rightward shift. Thus increased CO2 best explains the rightward shift with increased metabolic activity.