Physiology
Oxygen-Haemoglobin Dissociation Curve
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Get access- Sigmoid shape: oxygen binding alters the protein shape to promote binding
- Increased dissociation (curve moves right):
- CO2 rise
- Temperature rise
- pH decreased (hydrogen ion rise)
- Increased 2,3-DPG
- Fetal haemoglobin has a higher affinity for oxygen: the curve lies left
- Myoglobin has a higher affinity for oxygen cp. haemoglobin
- Carbon monoxide has a very steep dissociation curve: can displace oxygen from haemoglobin
- Methaemoglobin has no affinity for oxygen
Deoxygenated haemoglobin forms carbamino compounds more readily and so venous blood is more efficient at transporting carbon dioxide
- 5% of CO2 is dissolved in plasma
- 90% travels as bicarbonate
- Carbonic anhydrase is found within red blood cells, not plasma
Haemoglobin
- Derivative of porphyrin
- Contains ferrous iron (Fe2+)
- Oxidation of iron to ferric iron, Fe3+, occurs in methaemoglobinaemia
- Globin: four polypeptide chains
- HbA: two alpha chains and two beta chains
HbF: two alpha chains and two gamma chains (fetal Hb has a higher O2 affinity)