Acidosis results in a shift of the oxygen dissociation curve to the:

• A. No shift
• B. Left
• C. Right
• D. Upward

Answer: (C)

Acidosis lowers pH and increases hydrogen ion concentration, which reduces hemoglobin’s affinity for oxygen (the Bohr effect). This causes the oxyhemoglobin dissociation curve to shift to the right, so at any given PO2, hemoglobin releases more oxygen to tissues. This enhanced unloading helps meet the greater metabolic demands during acidosis or high activity. Leftward shifts occur with alkalosis, cooler temperatures, or lower 2,3-BPG, which increase oxygen affinity and hinder unloading. An upward shift isn’t a standard way to describe these changes—the relevant description is a rightward shift.