Bohr effect

• Haemoglobin

  A globular protein, has four polypeptide chains in its quaternary structure
• Haemoglobin

  • Has four haem groups that each have an iron ion making it conjugated
  • Each haemoglobin molecule can carry four oxygen molecules
• One molecule of haemoglobin can combine with four molecules of oxygen, creating oxyhemoglobin in a reversible reaction
• Haemoglobin structure

  Undergoes conformation, making the molecule more exposed so that the other haem group can bind with oxygen
• The oxygen dissociation curve is non linear
• At low partial pressures of oxygen


  Haemoglobin has a low affinity for oxygen
• Once one molecule of oxygen is bound

  The affinity increases
• The quaternary structure of the haemoglobin changes


  Making the haemoglobin groups have a higher affinity for oxygen
• Binding more oxygen molecules


  Now requires a smaller increase in partial pressure
• The fourth haem group

  Only binds with oxygen at high partial pressure as all of the groups have been filled, making it less likely for oxygen to collide with the haem group
• Oxygen dissociation curve


  Sigmoidal curve
• Left shift on oxygen dissociation curve


  Fetal haemoglobin
• Fetal haemoglobin

  Needs to have higher affinity so that more oxygen can be taken up by RBCs
• The higher the saturation of oxygen in the haemoglobin


  The easier oxygen becomes to intake
• Haemoglobin very rarely often never reach 100% saturation
• As RBCs make their way out of the lungs and into tissues


  The partial pressure of oxygen decreases because tissues take up oxygen for respiration
• CO2 diffusion

  1. Diffuses from respiring cells as a waste product to the capillary into the blood plasma

  2. Diffuses into the red blood cell

  3. Water (H2O) in the RBC combines with the CO2 creating carbonic acid

  4. Carbonic anhydrase (enzyme) breaks down the carbonic acid into hydrogen and hydrogen carbonate

  5. Haemoglobin acts as a buffer and maintains the pH by getting rid of the hydrogen

  6. Hydrogen carbonate is released from the cell and is replaced by chloride (Cl-) ions to balance the charges (chloride shift)

  7. Oxygen is then released to respiring cells
• The erythrocyte does not have many organelles so it is suited for larger amounts of CO2 and O2 to diffuse into it
• how is CO2 transported?

  dissolved in blood plasma, combine with haemoglobin amino groups (carbaminohaemoglobin) and converted to hydrogen carbonate ions in RBCs.