co2 02

• Hemoglobin


  Molecule found in large quantities in red blood cells that transports both oxygen and carbon dioxide
• Hemoglobin dissociation curve


  Graph of percentage saturation against partial pressure of oxygen
• Higher partial pressure of oxygen


  Higher percentage saturation of hemoglobin with oxygen
• High partial pressure of oxygen


  Occurs at the capillaries in lungs
• Low partial pressure of oxygen


  Occurs in respiring tissues
• Hemoglobin dissociation curve


  • It is an S-shaped curve, not a straight line
  • This is due to cooperative binding or allosteric effects of hemoglobin
• The first oxygen molecule binding to hemoglobin changes its shape, increasing the affinity for the second and third oxygen molecules</b>
• When all hemoglobin binding sites are occupied, the curve levels off
• Ball effect


  High partial pressure of CO2 decreases the affinity of hemoglobin for oxygen
• High partial pressure of CO2


  Shifts the hemoglobin dissociation curve to the right
• At high CO2 concentration, more oxygen is needed to reach the same percentage saturation of hemoglobin
• Transport of CO2


  1. 85% as bicarbonate ions

  2. 5% dissolved in plasma

  3. 10% as carbaminohemoglobin
• Transport of CO2 in lungs


  1. Hemoglobin releases hydrogen ions, forming carbonic acid which then dissociates into CO2 and water

  2. Dissolved CO2 in plasma diffuses into alveoli

  3. CO2 from carbaminohemoglobin also diffuses into alveoli
• Carbonic anhydrase catalyses the conversion of CO2 and water to carbonic acid, and the reverse reaction
• The transport of oxygen and CO2 are highly intertwined processes