Oxygen dissociation curves

HideShow resource information
View mindmap
  • Oxygen dissociation curves
    • Curves
      • When haemoglobin is exposed to different partial pressures of oxygen it does not absorb the oxygen evenly.
      • At very low conc of oxygen the four polypeptides of the haemoglobin molecule are closely united and so it is difficult to absorb the first oxygen.
      • Once loaded this oxygen molecule causes the polypeptides to load the remaining three oxygen molecules very easily
      • The graph of this relationship is known as the oxygen dissociation curve.
      • The further the left the curve is the greater the affinity of haemoglobin for oxygen (so it takes up oxygen less easily)
      • The further to the right the curve is the lower the affinity of haemoglobin for oxygen (so it takes up oxygen less readily but releases it more easily)
    • Effects of oxygen concentration (Bohr effect)
      • Haemoglobin has a reduced affinity for oxygen in the presence of carbon dioxide.
      • The greater the conc of carbon dioxide the more readily haemoglobin the more readily the haemoglobin releases its oxygen.
      • At the gas exchange surface the level of carbon dioxide is low because it diffuses across the exchange surface.
        • The affinity of haemoglobin for oxygen is increased which coupled with the high conc of oxygen in the lungs, means the oxygen is readily loaded by haemoglobin which shifts the curve to the left
      • In rapidly respiring tissues the level of carbon dioxide is high. The affinity of haemoglobin is reduced
        • This means oxygen is readily unloaded from the haemoglobin into the muscle cells. The increased CO2 level has shifted the curve to the right
      • The greater the conc of CO2 the more readily oxygen is released this is because  dissolved CO2 is acid and the low pH causes haemoglobin to change shape.
    • Loading, transport and unloading of oxygen
      • At the gas exchange surface carbon dioxide is constantly being removed
      • The pH is raised due to the low level of CO2
      • The higher pH changes the shape of haemoglobin into one that enables it to load oxygen readily
      • This shape also increases the affinity do it id not released while being transported in the blood to the tissues. In the tissues CO2 is produced by respiring cells
      • CO2 is acidic in solution so the pH is lowered. The lower pH changes the shape of haemoglobin into one with a lower affinity
      • Haemoglobin releases its O2 into the respiring tissues

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Biological molecules, organic chemistry and biochemistry resources »