The effect of CO2 concentration on oxygen

• Explain what happens to the partial pressure of oxygen when there is a high partial pressure of carbon dioxide?

  -if CO2 concentration increases, more oxygen disassociates from oxyhaemoglobin

  -the oxygen disassociation curve shifts to the right (a higher oxygen concentration is required to saturate haemoglobin due to H+ competition)

  -this is the Bohr effect
• Outline the effect of CO2 concentration on haemoglobin's affinity for oxygen.?

  -in respiring tissues, O2 levels are low and CO2 levels are high

  -CO2 dissolves, producing carbonic acid, thus reducing the pH of the blood

  -carbonic acid is split into H+ and hydrogen carbonate ions

  -haemoglobin has a lower O2 affinity at a lower pH, because H+ displaces the oxygens on the haem groups

  -blood will release more O2 to the tissues
• Describe how CO2 is transported from respiring tissues to the lungs.?

  5% gets dissolved in plasma

  10% forms carbamino-haemoglobin

  85% gets transported as hydrogen carbonate ions:

  CO2 diffuses into the RBC and dissolves in water to form carbonic acid (catalysed by the enzyme carbonic anhydrase)

  Carbonic acid disassociates into H+ and HCO3-

  Hydrogen carbonate ions diffuse into blood plasma

  Chloride ions diffuse into the cell by chloride shift to maintain the electrochemical neutrality of the cell
• Explain how changes in CO2 concentration in the blood can lead to an increased oxygen supply for respiring tissues.?

  -respiring tissues increase the CO2 concentration in the blood

  -this causes more carbonic acid to be made by CO2 dissolving in water

  -this lowers the pH of the blood and makes more H+ ions

  -because haemoglobin has a higher affinity for hydrogen than oxygen, oxygen is released more readily from oxyhaemoglobin

  -this causes the oxygen disassociation curve to move to the right