Which statement correctly describes the Bohr effect?

Which statement correctly describes the Bohr effect?

• A. The curve shifts left with alkalosis
• B. The curve shifts left with acidosis
• C. The curve shifts right with alkalosis
• D. The curve shifts right with hypocarbia

Answer: (A)

The Bohr effect describes how changes in pH and CO2 levels alter hemoglobin’s affinity for oxygen. When the pH rises (alkalosis) or CO2 falls (hypocarbia), hemoglobin binds O2 more tightly, shifting the oxyhemoglobin dissociation curve to the left. This means higher oxygen affinity and less unloading of O2 at tissues, which facilitates loading of O2 in the lungs where CO2 is being expelled and pH is rising. In contrast, acidosis (lower pH, higher CO2) pushes the curve to the right, decreasing O2 affinity and promoting unloading of O2 at tissues that are metabolically active with high CO2 production. Hypocarbia tends to shift the curve to the left, not to the right. Thus, alkalosis causes a leftward shift of the curve, making it the correct description.

The Bohr effect describes how changes in pH and CO2 levels alter hemoglobin’s affinity for oxygen. When the pH rises (alkalosis) or CO2 falls (hypocarbia), hemoglobin binds O2 more tightly, shifting the oxyhemoglobin dissociation curve to the left. This means higher oxygen affinity and less unloading of O2 at tissues, which facilitates loading of O2 in the lungs where CO2 is being expelled and pH is rising.

In contrast, acidosis (lower pH, higher CO2) pushes the curve to the right, decreasing O2 affinity and promoting unloading of O2 at tissues that are metabolically active with high CO2 production. Hypocarbia tends to shift the curve to the left, not to the right.

Thus, alkalosis causes a leftward shift of the curve, making it the correct description.