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  • Created by: Laura
  • Created on: 17-04-14 11:33
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  • Haemoglobin
    • Haemoglobin molecules
      • The haemoglobins are a group of chemically similar molecules found in a wide variety of organisms
      • Primary structure (chain of amino acids) - concisting of four polypeptide chains
      • Secondary structure - in which each of these polypeptide chains is coiled into a helix or pleated sheet
      • Tertiary structure - in which each polypeptide chain is folded into a precise shape, an important factor in its ability to carry oxygen (ionic, hydrogen and sulphur bonds)
      • Quaternary structure - in which all four polypeptides are linked together to form an almost spherical molecule.
      • Each haem group binds with an oxygen molecule as they contain ion. In humans they can carry four O2.
    • The role of Haemoglobin
      • The role of it is to transport oxygen
      • To do this oxygen must readily associate with oxygen at the surface where gas exchange takes place and readily dissociate with it at the tissues requiring it
      • Haemoglobin can change its affinity for oxygen under different conditions.
      • It does this by changing its shape in the presence of a certain substance, such as carbon dioxide.
      • In the presence of carbon dioxide, the new shape binds more loosely with oxygen so as a result haemoglobin releases its oxygen
    • Why have different haemoglobins?
      • There are different types of haemoglobin. These exhibit different properties relating to the way they took up and release oxygen
      • Haemoglobins with a high affinity for oxygen take up oxygen more easily but release it less readily
      • Haemoglobins with a low affinity for oxygen take up oxygen less readily but release it more readily
      • Correlation between type of haemoglobin possessed and its surrounding environment or its metabolic rate.
        • An organism living in an environment with little oxygen requires a haem that readily combines with oxygen if it is to absorb enough of it. Provided the fact it has a low metabolic rate
        • An organism with a high metabolic rate needs to release oxygen readily into its tissues. Provided that there is plenty of oxygen in the air.
    • Process of haemoglobin combining with oxygen is called loading or associating and it happens in the lungs
    • Process of haemoglobin releasing oxygen is called unloading or dissociating which takes place in the tissues


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