The Bohr Shift (AQA AS Biology): Revision Note

The Bohr effect

• The concentration of carbon dioxide in the blood influences the dissociation of oxyhaemoglobin; this change is known as the Bohr effect, or Bohr shift

• The Bohr effect occurs as follows:

  1. respiration produces carbon dioxide as a waste product

  2. partial pressure of carbon dioxide (pCO₂) in the blood is high

  3. haemoglobin’s affinity for oxygen is reduced

  4. dissociation of oxyhaemoglobin increases

  5. availability of oxygen increases

• The Bohr effect is greatest in actively respiring tissues, meaning that haemoglobin gives up its oxygen more readily in the respiring tissues where it is needed

• At higher pCO₂ the oxyhaemoglobin dissociation curve shifts to the right

  • This indicates that at any given partial pressure of oxygen, the percentage saturation of haemoglobin is lower at higher levels of CO₂