Oxygen Transport

• Functions of the blood

  • Transporting oxygen and carbon dioxide
  • Carrying hormones in the plasma and transporting waste which dissolves in the plasma to the kidney
  • Defending against pathogens using white blood cells, phagocytes, lymphocytes, antibodies and antitoxins
  • Thermoregulation which is regulation of the body temperature
• Components of the blood


  • Red blood cells (contain haemoglobin, biconcave, flexible and have no nucleus)
  • Phagocytes which defend and contain enzymes
  • Lymphocytes which produce antibodies and antitoxins
  • Platelets which work by rupturing and realising an enzyme near the cut which results in reactions that convert soluble blood protein fibrinogen to insoluble fibrin threads which trap the blood cells and platelets to form a blood clot
• Red blood cells (erythrocytes)

  Carry blood from highly saturated areas such as the lungs to low saturated areas such as the muscles
• Dissociation


  The release of oxygen from the red blood cell
• Each haemoglobin can carry 4 oxygens
• oxygen-haemoglobin dissociation curve

  • The shape is due to the shape of the haemoglobin molecule making it difficult for the first oxygen to bind, but as the first one binds, the change in shape causes the other oxygen molecules to bind more easily (positive cooperativity)
  • The 1st and 4th oxygens are hard to bind
• Affinity of haemoglobin for oxygen


  • Increases with higher pH, lower temperature and lower carbon dioxide (further to the right and up on the graph)
  • Decreases with lower pH, higher temperature and higher carbon dioxide (further to the left and down on the graph)
• Bohr effect


  The greater the concentration of carbon dioxide, the easier the red blood cells unload oxygen, and vice versa
• • In the lungs, the concentration of carbon dioxide is low and therefore the red blood cells take in more oxygen and release less
  • In the muscles, the carbon dioxide concentration is higher and therefore the red blood cell releases oxygen more easily and makes it in less easily
• pH affects the shape of haemoglobin, when it is higher, it causes the affinity for oxygen to increase, and when it is lower, it causes the affinity for oxygen to decrease
• Carbon dioxide causes pH to slightly increase when there is less, and slightly decrease when there is more, because carbon dioxide forms carbonic acid in solution
• Haemoglobin molecules


  • Primary structure: sequence of amino acids in the 4 polypeptide
  • Secondary structure: each polypeptide chain is coiled into a helix
  • Tertiary structure: each polypeptide chain is folded into a precise shape - important factor in its ability to carry oxygen
  • Quaternary structure: all 4 polypeptides are linked together to form an almost spherical molecule, each associated with a heme group containing a ferrous (Fe2+) ion that can bind to 1 oxygen molecule
• Loading / associating


  Haemoglobin binds with oxygen (takes place in lungs)
• Unloading / dissociating


  Haemoglobin releases its oxygen (takes place in tissues)
• Role of haemoglobin


  To transport oxygen efficiently by readily associating with oxygen at the surface where gas exchange takes place, and readily dissociating from oxygen at those tissues requiring it