Haemoglobin

• What is haemoglobin?

  A globular protein with a quaternary structure in erythrocytes
• What are some distinct features of haemoglobin?

  • Has 4 subunits - 2 alpha & 2 beta chains
  • Has four haem groups - prosthetic groups with Fe+
• Process of Oxygen Transport:

  • Haemoglobin picks up oxygen at capillaries in the lungs
  • Oxygen binds to iron in haem group forming oxyhaemoglobin
  • Each haemoglobin can carry up to four molecules of oxygen at a time
  • Oxyhaemoglobin is transported to respiring tissues via the blood
  • Oxygen dissociates at the body tissues
• What is partial pressure?

  The pressure exerted by a single gas in a mixture of gases.
• What is the partial pressure of oxygen?

  20 kPa
• What happens to haemoglobin at higher partial pressures of oxygen?

  Haemoglobin has a high affinity of oxygen & binds with it (e.g. in the lungs)
• What happens to haemoglobin at lower partial pressures of oxygen?

  Haemoglobin has a lower affinity for oxygen and releases it (e.g. in body cells)
• What is the difference between fetal and adult haemoglobin?

  Fetal haemoglobin has a higher affinity for oxygen
• Why does fetal haemoglobin have a higher affinity for oxygen?

  It allows foetal haemoglobin to bind to oxygen at lower partial pressures (in the placenta)
• Explain the image:

  • Fetal haemoglobin curve shifts to the left
  • Fetal haemoglobin has higher affinity for oxygen
  • At any given partial pressure, fetal haemoglobin will have higher % saturation

  
• What is cooperative binding in haemoglobin?

  As the haemoglobin binds to one oxygen molecule, it changes shape, making it easier to bind with other oxygen molecules
• What is the Bohr Effect?

  Haemoglobin has a lower affinity for oxygen at higher partial pressures of carbon dioxide
• Why does the Bohr Effect happen?

  • Active tissues release more carbon dioxide & need a lot of oxygen
  • At high partial pressures of carbon dioxide, haemoglobin has lower affinity for oxygen
  • Haemoglobin releases more oxygen
• Why do active tissues need more oxygen?

  For aerobic respiration
• How is carbon dioxide transported around the body?

  In the plasma, in haemoglobin & as hydrogen carbonate ions
• Process of Carbon Dioxide Transport:

  • Carbon dioxide diffuses from plasma into erythrocytes
  • The CO2 combines with water in the cell to make carbonic acid
  • The reaction is catalysed by carbonic anhydrase
  • The carbonic acid dissociates into H+ and HCO3- ions
  • H+ ions combine with haemoglobin to make haemoglobinic acid
  • The HCO3- ions diffuse out of the red blood cell into the plasma & are transported around the body
• What does the haemoglobinic acid do in carbon dioxide transport?

  Act as a buffer, stopping H+ ions from lowering pH in red blood cells
• What is the Chloride Shift?

  When Cl- ions diffuse into the red blood cell after carbon dioxide transport to maintain charge balance
• How can altitude affect haemoglobin?

  At high altitudes, the ppO2 is lower, so species living in these conditions may have haemoglobin that is adapted and can easily bind to oxygen (e.g. llamas)