The Bohr Shift
- Changes in the oxygen dissociation curve as a result of carbon dioxide levels are known as the Bohr effect, or Bohr shift
- When the partial pressure of carbon dioxide in the blood is high, haemoglobin’s affinity for oxygen is reduced
- This is the case in respiring tissues, where cells are producing carbon dioxide as a waste product of respiration
- This occurs because CO2 lowers the pH of the blood
- CO2 combines with water to form carbonic acid
- Carbonic acid dissociates into hydrogen carbonate ions and hydrogen ions
- Hydrogen ions bind to haemoglobin, causing the release of oxygen
- This is a helpful change because it means that haemoglobin gives up its oxygen more readily in the respiring tissues where it is needed
- On a graph showing the dissociation curve, the curve shifts to the right when CO2 levels increase
- This means that at any given partial pressure of oxygen, the percentage saturation of haemoglobin is lower at higher levels of CO2
The Bohr effect diagram
The dissociation curve shifts to the right as a result of the Bohr effect. This means that any given partial pressure of oxygen, the percentage saturation of haemoglobin is lower at higher CO2 levels.