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Describe the structure of haemoglobin?
*Primary structure - 4 polypeptide chains.
*Secondary structure - Coiled into helix.
*Tertiary structure - Each polypeptide is folded into precise shape {to carry O2}.
*Quarternary structure - Polypeptide chains linked to form almost spherical molecule.
*Polypeptides each have Haem group & is a globular protein. Structure curled up so hydrophilic side chains face outwards & hydrophobic chains face inwards - Soluble - Good for transport in blood.
What types of haemoglobin are there?
*Haemoglobin with a high affinity for oxygen. These take up oxygen more easily but release less readily.
*Haemoglobin with a low affinity for oxygen. These take up oxygen less easily but release it more readily.
What is the role of haemoglobin & how much oxygen can a haem group hold?
*To transport oxygen, to do this it must:-
-> Readily associate with oxygen at the gas exchange surface.
-> Readily dissociate from oxygen at the tissue requiring it.
*1 oxygen molecule per haem group:-
Hb + 4O2 <-> Hb(O2)4
When does haemoglobin have a high affinity & a low affinity for oxygen?
*High affinity for oxygen at gas exchange surface so oxygen binds.
*Low affinity for oxygen at respiring tissues. High concentration of CO2 causes Hb to change shape, releasing oxygen.
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