What term describes the shift in haemoglobin-oxygen affinity due to increased CO2 and decreased pH during exercise?

What term describes the shift in haemoglobin-oxygen affinity due to increased CO2 and decreased pH during exercise?

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

Answer: (B)

During exercise, tissues produce more CO2 and lactic acid, lowering pH and increasing hydrogen ion concentration. This reduces haemoglobin’s affinity for oxygen, so oxygen is released more readily to the working muscles. This is known as the Bohr shift. On the haemoglobin-oxygen dissociation curve, higher CO2 and H+ cause a rightward shift, meaning at any given partial pressure of oxygen, haemoglobin is less saturated and unloads more O2 where it’s needed. The mechanism involves CO2 entering red blood cells and forming carbonic acid, which dissociates into bicarbonate and H+. The extra H+ binds to haemoglobin, stabilising the deoxygenated form and reducing O2 affinity. Increased muscle temperature during exercise also promotes this effect, further aiding O2 delivery to active tissues. This adaptation helps meet the muscles’ higher metabolic demand. Other terms describe different ideas: the general process of oxygen binding/dissociation, blood flow bypass mechanisms, or oxygen extraction measurements, none of which capture the shift in affinity caused by CO2 and pH changes during exercise.

During exercise, tissues produce more CO2 and lactic acid, lowering pH and increasing hydrogen ion concentration. This reduces haemoglobin’s affinity for oxygen, so oxygen is released more readily to the working muscles. This is known as the Bohr shift. On the haemoglobin-oxygen dissociation curve, higher CO2 and H+ cause a rightward shift, meaning at any given partial pressure of oxygen, haemoglobin is less saturated and unloads more O2 where it’s needed.

The mechanism involves CO2 entering red blood cells and forming carbonic acid, which dissociates into bicarbonate and H+. The extra H+ binds to haemoglobin, stabilising the deoxygenated form and reducing O2 affinity. Increased muscle temperature during exercise also promotes this effect, further aiding O2 delivery to active tissues.

This adaptation helps meet the muscles’ higher metabolic demand. Other terms describe different ideas: the general process of oxygen binding/dissociation, blood flow bypass mechanisms, or oxygen extraction measurements, none of which capture the shift in affinity caused by CO2 and pH changes during exercise.