bohr's effect

• Bohr effect

  The effect of carbon dioxide on the oxygen affinity of haemoglobin
• Oxygen transport by haemoglobin

  1. Haemoglobin has 4 polypeptide chains

  2. Each chain contains a haem group

  3. Each haem group can bind 1 oxygen molecule

  4. 1 haemoglobin molecule can bind up to 4 oxygen molecules
• Oxygen dissociation curve


  Graph showing percentage saturation of haemoglobin with oxygen against partial pressure of oxygen
• Partial pressure of oxygen is high in alveoli


  Haemoglobin has high affinity for oxygen
• Partial pressure of oxygen decreases in tissues


  Haemoglobin unloads oxygen
• Partial pressure of carbon dioxide increases in tissues


  Haemoglobin affinity for oxygen decreases (Bohr effect)
• Bohr effect

  Carbon dioxide causes the oxygen affinity of hemoglobin to decrease
• Partial pressure of carbon dioxide is low in lungs


  Haemoglobin has high affinity for oxygen
• Partial pressure of carbon dioxide is high in active tissues


  Hemoglobin has lower affinity for oxygen, so more oxygen is unloaded
• Carbon dioxide transport in blood

  1. Carbon dioxide forms carbonic acid

  2. Carbonic acid releases hydrogen ions

  3. Hydrogen ions combine with hemoglobin

  4. This changes hemoglobin's quaternary structure

  5. Reducing hemoglobin's affinity for oxygen