Has 4 subunits. Each consists of a polypeptide chain and a haem group.
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What does the haem group contain and what will this do?
A single iron atom (Fe2+). The iron ion can attract and hold an oxygen molecule.
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What is this attraction called?
Affinity. Haem group has an affinity for oxygen.
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How many oxygen molecules can each haem group hold?
Each haem group can hold 1 oxygen molecule. Each haemoglobin molecule can therefore carry 4 oxygen molecules.
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How does haemoglobin take up oxygen?
Oxygen is absorbed into the blood in the lungs. Oxygen diffuses into the blood plasma and enters the red blood cells. They can be taken up by haemoglobin.
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What is it called when oxyhaemoglobin releases oxygen? And what is this oxygen needed for?
Release of oxygen is called dissociation. The cells need oxygen for aerobic respiration.
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How is the amount of oxygen measured?
By the partial pressure, measured in KPa.
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What shaped curve does haemoglobin taking up oxygen produce?
An S-shaped curve.
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What is this curve called?
The oxyhaemoglobin dissociation curve.
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When does the haemoglobin not readily take up oxygen molecules?
At low oxygen tension/partial pressure.
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Why does haemoglobin not readily take up oxygen at low partial pressures?
The haem groups are in the centre of haemoglobin, making it difficult for the oxygen to reach the haem group and associate.
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What happens as the partial pressure rises?
The diffusion gradient into the haemoglobin molecule increases.
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What is the change in the shape of the curve called when an oxygen molecule associates with a haem group in haemoglobin?
Conformational change.
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What does this conformational change when oxygen associates allow?
Allows more oxygen to diffuse into the haemoglobin molecule and associate with other haem groups. This accounts for the steepness of the curve.
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What happens once the haemoglobin molecule contains 3 oxygen molecules?
It becomes hard for the 4th molecule to diffuse in and associate with the last available haem group.
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What does this mean?
It is difficult to achieve 100% saturation of all the haemoglobin, even when the oxygen tension/partial pressure is very high.
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What odes this difficulty cause the curve to do?
Causes the curve to level off as the saturation approaches 100%.
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What does the fetal haemoglobin have a higher affinity for?
Higher affinity for oxygen than adult haemoglobin does.
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Where is the dissociation curve for fetal haemoglobin on the dissociation curve compared to adult haemoglobin?
Fetal haemoglobin curve is to the left of the adult haemoglobin curve.
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Describe why the fetal haemoglobin curve is to the left of the adult haemoglobin curve (4)
Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin does. Fetal haemoglobin can take up oxygen at lower partial pressures. The placenta has a low partial pressure of oxygen.
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What will happen to adult haemoglobin at low partial pressures of oxygen?
Adult haemoglobin will dissociate at lower partial pressures of oxygen.
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Other cards in this set
Card 2
Front
Describe haemoglobin
Back
Has 4 subunits. Each consists of a polypeptide chain and a haem group.
Card 3
Front
What does the haem group contain and what will this do?
Back
Card 4
Front
What is this attraction called?
Back
Card 5
Front
How many oxygen molecules can each haem group hold?
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