An increase in blood CO2 and a decrease in pH reduces haemoglobin's affinity for oxygen. What is this effect called?

• A. Oxyhaemoglobin Dissociation
• B. Bohr shift
• C. A-VO2 Difference
• D. Vascular Shunt Mechanism

Answer: (B)

The Bohr effect explains how increased CO2 and a fall in pH reduce haemoglobin’s affinity for oxygen, causing the oxygen–haemoglobin dissociation curve to shift to the right. This means haemoglobin releases more oxygen to tissues that are producing CO2 and H+, such as active muscles. In the lungs, CO2 is expelled and pH rises, shifting the curve left to aid oxygen loading. The described situation directly matches this rightward shift, so Bohr shift is the best term. The other options describe different concepts: the general process of oxygen binding/release, the amount of oxygen extracted by tissues, and the routing of blood, none of which capture this CO2- and pH-driven change in Hb affinity.