Haemoglobin Revision page

Here i have written out a short, easy to understand  summary page of the rather confusing and tricky topic which is Haemoglobins.

Hope it helps you get to grips with what its used for and its function!

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Haemoglobins a protein that carries oxygen round the body!
Different species have different versions of it depending on where they live.
1) Red blood cells contain haemoglobin
2) Haemoglobin is a large protein with a quaternary structure (four polypeptide chains)
3) Each chain has a Haem group which contains iron (this gives the haemoglobin its red colour)
4) Haemoglobin has a high affinity for oxygen! Each molecule can carry four oxygen molecules.
5) In the lungs, oxygen easily joins to haemoglobin in red blood cells to form oxyhaemoglobin.
Hb -> 4O2 <->HbO8 (its reversible)
Haemoglobin saturation depends on the partial pressure of oxygen
The partial pressure of oxygen (pO2) is a measure of the oxygen concentration. (the greater the
concentration of dissolved oxygen in cells, the higher the partial pressure)
Similarly, the pCO2 is a measure of Carbon dioxide in a cell.
Oxygen loads onto haemoglobin to form oxyhaemoglobin where there's a high pO2.
Oxyhaemoglobin unloads its oxygen where there's a lower pO2
Oxygen enters blood capillaries at the alveoli in the lungs. Alveoli have a high pO2, therefore oxygen
loads onto haemoglobin to form oxyhaemoglobin.
When cells respire, they use up oxygen- this lowers the pO2. Red blood cells deliver oxyhaemoglobin
to the respiring tissues, where it unloads its oxygen.
Haemoglobin then returns to the lungs to pick up more oxygen.
Dissociation Curves show how Affinity for Oxygen varies
Where pO2 is high (in the lungs) haemoglobin has a high affinity for oxygen (it will readily combine
with oxygen. So it has a high saturation of oxygen.
Where pO2 is low (in respiring tissues) haemoglobin has a low affinity for oxygen that means it
releases oxygen rather that combining with it. So it has a low saturation of oxygen.
100% saturation means every haemoglobin molecule is carrying the maximum of 4 oxygen molecules!
The graph is `S-shaped' because when haemoglobin combines with the first oxygen molecule, its shape
alters in a way that makes it easier for other molecules to join too. But as haemoglobin becomes more
saturated it gets harder for more oxygen molecules to join. The curve has a steep in the middle where
it's easy for Oxygen molecules to join and shallow bits where its harder.
Carbon Dioxide concentration affects Oxygen unloading
Haemoglobin gives up its oxygen more readily at higher partial pressures of Carbon Dioxide
1) When cells respire they produce carbon dioxide, this raises pCO2
2) This increases the rate of oxygen unloading- more oxygen's being released
3) This is called the Bohr effect.
Haemoglobin is different in different organisms
1) Organism's that live in environments with a low concentration of oxygen have haemoglobin with a
higher affinity for oxygen than human haemoglobin-the dissociation curve is to the left of ours.
2) Organisms that are very active and have a high oxygen demand have haemoglobin with lower
affinity for oxygen than human haemoglobin-the curve is to the right of ours.

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