The Variety Of Life Continued
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The Variety Of Life Continued

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The Variety Of Life Continued The Variety Of Life Continued Presentation Transcript

  • The variety of life continued 3.2.4
  • Haemoglobin continued
    • On investigating how Haemoglobin joined with oxygen it was discovered that there were different types.
    • The differences were to do with how they took up and released oxygen.
  • Haemoglobin continued
    • Haemoglobins with a high affinity for oxygen. Take it up easily but release less readily.
    • and Haemoglobins with a low affinity for oxygen. Not as easy to take up but release readily.
  • Why might this be?
  • Why different types?
    • There is a correlation between the affinity for oxygen and factors such as environment in which the organisms lived or its metabolic rate.
    • In an oxygen poor area the haemoglobin will need a much higher affinity for oxygen.
    • If the metabolic rate is high oxygen needs to be given to the tissues very easily .
  • What causes these different affinities? Different shaped caused by differences in the amino acid sequence.
  • Haemoglobin combining with oxygen is called loading or associating and in humans happens in the lungs.
  • Haemoglobin releasing oxygen is called unloading or dissociating and in humans happens in the tissues.
  • Oxygen dissociation curves.
  • Oxygen dissociation curves.
    • Haemoglobin does not absorb oxygen evenly at all partial pressures.
    • ( The amount of gas is measured by how much pressure it contributes to the total pressure of the gas mixture, and is measured in kiloPascals (kPa))
    • The shape of the molecule changes as the partial pressures of gases varies.
  • Oxygen dissociation curves.
    • The shape of the molecule changes as the partial pressures of gases varies.
    • At very low oxygen concentrations the 4 polypeptides are closely united making it difficult to absorb the first oxygen molecule.
    • But once the first is loaded it becomes very easy to load the rest.
  • A very small decrease in the partial pressure of oxygen leads to a lot of oxygen becoming dissociated from the haemoglobin
  • Why does the graph tail off at very high concentrations? The haemoglobin is almost saturated .
  • As there are many different types of haemoglobin and respond to different conditions many oxygen dissociation curves exist but they all have the same basic shape.
  • Effect of CO 2 concentration
    • Carbon dioxide reduces the affinity for oxygen (this helps oxygen get where it is needed)
    • The greater the concentration of carbon dioxide the more readily it releases its oxygen (the Bohr effect)
  • Effect of CO 2 concentration
    • The greater the concentration of carbon dioxide the more readily it releases its oxygen (the Bohr effect)
    • At the gas-exchange surface carbon dioxide levels are low and the affinity for oxygen is high. This combined with the high levels of oxygen means it is readily loaded by haemoglobin.
  •  
  • Effect of CO 2 concentration
    • At the gas-exchange surface carbon dioxide levels are low and the affinity for oxygen is high. This combined with the high levels of oxygen means it is readily loaded by haemoglobin.
    • In rapidly respiring tissues the levels of carbon dioxide is high. This reduces the affinity of haemoglobin for oxygen in the muscles, so the oxygen is readily unloaded.
  • Dissolved carbon dioxide is acidic and this low ph is what causes the haemoglobin to change shape.
  • Loading, transport and unloading of oxygen
    • Carbon dioxide is constantly being removed at gas exchange surfaces so the pH is higher
    • As the pH changes the shape of the haemoglobin changes effecting oxygen affinity.
    • At the respiring tissues carbon dioxide is produce lowering the pH.
    • Haemoglobin changes shape of oxygen is lost.
  • This is useful as it makes sure each tissue gets the right amount of oxygen. More active tissue produces more carbon dioxide and needs more oxygen.
  • Other organisms
  • Where you live is important
    • The Lugworm is not very active and spends most of its life in a U-shaped burrow.
    • It is normally covered by sea water which it circulates through its burrow.
    • Oxygen diffuses into the lugworm’s blood from the water and is transported by haemoglobin.
  • Lugworms
    • When the tide it out the lugworm can not circulate fresh supply of oxygenated water through its burrow.
    • The water has very little oxygen as the lugworm continues to use it up.
    • So ALL the oxygen in the water needs to be extracted.
    • Because of this the Lugworm can saturate its haemoglobin at a very low partial pressure of oxygen
  • Answer green question 1-6 on page 155
  • Size matters
    • Mice has a large surface area to volume ratio (small animals).
    • Consequently they lose body heat rapidly.
    • To make up for this they have a high metabolic rate that generates heat and helps them to maintain their normal body temperature.
  • Because of this the curve is shifted to the right.
  • Activity counts.
    • Flight in birds and swimming in fish are both energy demanding.
    • Flight muscles have a high metabolic rate and during light, much of the blood pumped by the heart goes to these muscles.