d r e a m y
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Am I right in saying haemoglobin is able to readily associate oxygen at low partial pressures of oxygen? Because someone told me that instead it's able to associate oxygen at high partial pressures of carbon dioxide
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thedentchlox
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By looking at the oxygen dissociation curve, it will really help. At low partial pressure of oxygen, the haemoglobin cannot associate with oxygen as the haem groups are in the centre of the molecule not the outskirts.
When theres high pp of carbon dioxide, the affinity for oxygen is lower in haemoglobin as carbon dioxide lowers the pH so oxygen can no longer bind to haemoglobin due to changes in its structure
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d r e a m y
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(Original post by thedentchlox)
By looking at the oxygen dissociation curve, it will really help. At low partial pressure of oxygen, the haemoglobin cannot associate with oxygen as the haem groups are in the centre of the molecule not the outskirts.
When theres high pp of carbon dioxide, the affinity for oxygen is lower in haemoglobin as carbon dioxide lowers the pH so oxygen can no longer bind to haemoglobin due to changes in its structure
Can I ask, why is the shape sigmoid?
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lhh2003
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(Original post by d r e a m y)
Can I ask, why is the shape sigmoid?
At a low pO2 , the Haemoglobin molecule's Haem groups are 'inverted' inwards. They are not accessible to oxygen molecules to bind with them, giving a low saturation of Haemoglobin with O2.. However, when as little as one Haem group of a Haemoglobin molecule "cooperatively binds" with an Oxygen molecule, the protein undergoes a conformational change, and the Haem groups get pushed outwards. This makes the curve drastically increase with even a slight increase in pO2. But eventually all Haem groups become saturated with Oxygen, and so they can bind with no more oxygen, so the graph flattens at 100% saturation at very high pO2.
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d r e a m y
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(Original post by lhh2003)
At a low pO2 , the Haemoglobin molecule's Haem groups are 'inverted' inwards. They are not accessible to oxygen molecules to bind with them. However, when as little as one Haem group of a Haemoglobin molecule "cooperatively binds" with an Oxygen molecule, the protein undergoes a conformational change, and the Haem groups get pushed outwards. This makes the curve drastically increase with even a slight increase in pO2. But eventually all Haem groups become saturated with Oxygen, and so they can bind with no more oxygen, so the graph flattens at 100% saturation at very high pO2.
Thank you!! so after the first oxygen molecule binds with haemoglobin, the structure is distorted? Does this make it easier for the other oxygen molecules to bind?
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lhh2003
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(Original post by d r e a m y)
Thank you!! so after the first oxygen molecule binds with haemoglobin, the structure is distorted? Does this make it easier for the other oxygen molecules to bind?
Exactly. All Haem groups initially face inwards, but if one Haem group manages to bind, the change described above occurs so the other Haem groups can bind more easily with oxygen that would have been facing inwards as they get pushed outwards.
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