Haemoglobin
- Created by: Manon Burbidge
- Created on: 23-04-13 17:52
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- Haemoglobin
- Structure of Haemoglobin
- Primary: Haemoglobin is made up of four polypeptide chains.
- Secondary: These polypeptide chains are wound and coiled into a helix.
- Tertiary: Each polypeptide is folded into a precise shape, vital for its ability to carry oxygen.
- Quartenary: All four polypeptides are linked to form a spherical molecule, and each is associated with a haem group which contains an iron ion.
- Role and Function
- Red blood cells contain haemoglobin, which has a varying oxygen affinity. Each polypeptide is associated with a haem group, and the iron ion in it can combine with 1 oxygen molecule: therefore each red blood cell can carry a total of 4 oxygen molecules.
- In the lungs, oxygen binds to haemoglobin to form oxyhaemoglobin. This is a reversible reaction, and when oxygen dissociates from it, it returns to being haemoglobin.
- To be efficient at transporting oxygen, haemoglobin must a) associate with oxygen readily where gas exchange takes place- in humans, the lungs. b) Readily dissociate from oxygen at the tissues requiring it
- Partial Pressure
- It is a measure of oxygen concentration. The greater the concentration of oxygen, the higher the partial pressure.
- Oxygen loads onto haemoglobin where there's high partial pressure and unloads where partial pressure is low.
- Alveoli in the lungs have high partial pressure so oxygen loads. Respiring cells release C02 which lowers the p02, so hameoglobin unloads its cells.
- Different Haemoglobin?
- Differences occur due to variation in shape due to slightly different sequences of amino acids.
- Haemoglobin with a high oxygen affinity: take up oxygen easily but release it less readily. Low affinity haemoglobin take up oxygen less easily but release it readily.
- Organisms in low oxygen environments require high affinity haemoglobin providing it has a low metabolism. Organisms with high metabolisms,in high oxygen environments require low affinity haemoglobin.
- Structure of Haemoglobin
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