Haemoglobin

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Haemoglobin

  • found in red blood cells
  • large globular protein with a quaternaru structure
  • each polypeptide chain has a haem group which contains iron
  • high infinity for oxygen
  • carries four oxygen molecules
  • oxygen + haemoglobin = oxyhaemoglobin

Where the partial pressure is low it has a low affinity for oxygen.

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the S shape is because the first O2 molecule to combine with haemoglobin makes it easier for the other molecules to join as its shape alters slightly.

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The Fetus

  • blood has a higher infinity for oxygen
  • recieve oxygen from mothers blood across the placenta
  • oxygen saturation decreases as it reaches fetus - therefor needs a higher affinity

Carbon Dioxide

  • haemoglobin gives up its oxygen more readily when there's a higher partial pressure of CO2
  • when cells respire they produce CO2
  • the CO2 is converted into carbonic acid by the enzyme carbonic anhydrase
  • carbonic acid splits up to form hydrogen irons and hydrogencarbonate irons
  • the increase in hydrogen ions causes oxyhaemoglobin to unload its oxygen so it can take up the hydrogen ions. - to form haemoglobinic acid
  • the hydrogencarbonate ions diffuse out the red blood cells and are transported in the blood plasma
  • in the lungs the C02 ions reform CO2 then diffuse into alveoli and are breathed out.
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