Haemoglobin

• Haemoglobin is an iron-containing protein that carries oxygen from the lungs to body tissues.
• Describe the structure of Haemoglobin.

  Quaternary Structure

  Composed of 4 polypeptides

  Each containing haem group - prosthetic

  Has an affinity to oxygen
• What is the partial pressure of oxygen

  The proportion of oxygen in a mixture of gases or a solution
• What is loading / association ?


  When oxygen is taken up by haemoglobin
• pO2 in lungs

  Partial pressure is high in capillaries

  Hb has a higher affinity for o2 at a high pO2

  Haemoglobin becomes almost fully saturated, passing through the capillaries - lungs
• pO2 in respiring tissues

  The pO2 in the tissue capillaries is lower

  Haemoglobin now has a lower affinity for O2 at a lower pO2 and so the oxyhaemoglobin starts to break down and unloads oxygen

  The oxygen released is then available to the tissue cells to be used in aerobic respiration
• Heat from respiration helps mammals to maintain a constant body temperature.

  Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen disassociation curves of their haemoglobins. (5)


  Smaller mammal has greater SA to - Vol ratio

  Smaller mammal more heat lost

  Smaller mammal greater rate of respiration

  oxygen required for aerobic respiration

  Haemoglobin releases more oxygen
• The oxygen disassociation curve of the foetus is to the left of that for its mother.

  Explain the advantage of this for the foetus.

  Higher affinity

  High partial pressure

  Oxygen moves from mother to foetus
• Explain how oxygen is loaded, transported and unloaded in the blood (6)

  Haemoglobin carries oxygen

  In erythrocyte

  Loading in lungs

  at high pO2

  releases into respiring cells

  at low pO2

  unloading linked to higher CO2 concentration
• Explain how changes in the shape of haemoglobin result in the S-shaped oxyhaemoglobin dissociation curve for HbA


  First oxygen binds causing change in shape

  Allows more O2 to bind
• Use the graph above to explain why this change is asdvantageous for the baby.

  It means there is a higher affinity for oxygen

  this will mean oxygen will disassociate from respiring cells
• Binding of one molecule of oxygen to haemoglobin makes it easier for a second to bind, explain how.

  The first O2 molecule to bind changes the tertiary structure of haemoglobin

  Exposing the 2nd and 3rd binding
• Formula for calculating the percentage saturation of haemoglobin with oxygen

  oxygenated haemoglobin / maximum saturation x 100
• High altitude / left

  Partial pressure of 02 at lungs is low

  Haemoglobin has a higher affinity to oxygen

  More O2 is loaded at lower partial pressures of oxygen

  This is then transported to the tissues

  For use in aerobic respiration
• Bohr Shift Right

  Increase in partial pressure of CO2 in the blood

  Oxygen dissociation curve shifts to the right

  Haemoglobin has a lower affinity for oxygen

  More O2 is unloaded at the tissue

  For use in aerobic respiration
• Small mammals and birds right

  Large SA : Vol ratio so loses heat more readily to environment

  Must increase rate of respiration to maintain boy temperature

  Haemoglobin has a lower affinity for oxygen

  More O2 is unloaded at the tissue

  For use in aerobic respiration