Mavs04
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Hi,
So I’ve got a few questions about these cos I rlly hAtE them they’re so hard:

1). My textbook and a sheet my teacher gave me contradict themselves, one says that further to the right oxygen molecules associate with haemoglobin more easily but the other says they associate less easily.
I thought that up until the 3rd O2 binds they do associate more easily but after that it’s harder due to the probability of finding an empty haem group (although in theory it should be easier). But I don’t get why it says further to the right the affinity for O2 is lower because this is to do with attraction not probability?

2). I don’t really understand how you’re actually supposed to interpret it, the top right is supposed to be the lungs but I thought the blood became oxygenated in the lungs, but apparently here it’s harder for haemoglobin to pick up oxygen due to it already being mostly saturated with it.
Also the bottom left is supposed to be cells respiring very heavily, so what is the steep bit in the middle? Cells respiring progressively less heavily??


Thanks for reading ik it’s quite long but as I said I’m rlly confused lol so any help would be appreciated!

Here’s a pic of one:Name:  AE6B3D4D-C41E-41AB-B7B5-128BD1DB8311.jpeg
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Last edited by Mavs04; 1 month ago
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0mitochondria
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The x axis is essentially what percentage of the air is oxygen. As the partial pressure increases the saturation increases as it is more likely that more oxygen will bind if there is more of it. This is why generally as the x axis increases, so does the y axis. The reason for the shape, is that the first molecule of oxygen is relatively difficult to bind, the 2nd and 3rd and easier and then the last one is the most difficult hence the plateau.

The bottom left is cells respiring heavily as they will use lots of O2 and produce lots of CO2 and so the partial pressure of O2 is low. As you said the top left is is in the lungs as there is a higher concentration of O2 as you have just breathed in.

Do you understand the Bohr effect and myoglobin/Fetal haemaglobin with respect to this curve?
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Mavs04
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(Original post by 0mitochondria)
The x axis is essentially what percentage of the air is oxygen. As the partial pressure increases the saturation increases as it is more likely that more oxygen will bind if there is more of it. This is why generally as the x axis increases, so does the y axis. The reason for the shape, is that the first molecule of oxygen is relatively difficult to bind, the 2nd and 3rd and easier and then the last one is the most difficult hence the plateau.

The bottom left is cells respiring heavily as they will use lots of O2 and produce lots of CO2 and so the partial pressure of O2 is low. As you said the top left is is in the lungs as there is a higher concentration of O2 as you have just breathed in.

Do you understand the Bohr effect and myoglobin/Fetal haemaglobin with respect to this curve?
Yeah I think I’m ok with the Bohr effect, the one where the CO2 concentration affects the pH which then affects the shape of haemoglobin and it’s affinity to oxygen?
We’ve not covered anything about fetal stuff yet tho.

Please could you explain about the affinity thing in my first post cos that’s what I rlly don’t understand?
Ty for replying!!
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mareena1
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(Original post by Mavs04)
Yeah I think I’m ok with the Bohr effect, the one where the CO2 concentration affects the pH which then affects the shape of haemoglobin and it’s affinity to oxygen?
We’ve not covered anything about fetal stuff yet tho.

Please could you explain about the affinity thing in my first post cos that’s what I rlly don’t understand?
Ty for replying!!
Generally animals that live in environments with less oxygen e.g llamas and fetuses need haemoglobin with a HIGHER affinity to oxygen to get enough oxygen for respiring tissues. As their haemoglobin has a higher affinity, it is more saturated at lower partial pressures of oxygen, therefore the dissasocciation curve shifts to the LEFT.
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0mitochondria
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So further to the right the affinity is higher, I think either your textbook or sheet was wrong, the affinity is high as there is lots of O2 so binds more easily. When less O2 it releases it, so less affinity. Also the steep bit in the middle is cells at rest. Does this help?
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mareena1
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(Original post by 0mitochondria)
So further to the right the affinity is higher, I think either your textbook or sheet was wrong, the affinity is high as there is lots of O2 so binds more easily. When less O2 it releases it, so less affinity. Also the steep bit in the middle is cells at rest. Does this help?
Im pretty sure further to the right affinity is lower
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Jpw1097
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(Original post by Mavs04)
Hi,
So I’ve got a few questions about these cos I rlly hAtE them they’re so hard:

1). My textbook and a sheet my teacher gave me contradict themselves, one says that further to the right oxygen molecules associate with haemoglobin more easily but the other says they associate less easily.
I thought that up until the 3rd O2 binds they do associate more easily but after that it’s harder due to the probability of finding an empty haem group (although in theory it should be easier). But I don’t get why it says further to the right the affinity for O2 is lower because this is to do with attraction not probability?

2). I don’t really understand how you’re actually supposed to interpret it, the top right is supposed to be the lungs but I thought the blood became oxygenated in the lungs, but apparently here it’s harder for haemoglobin to pick up oxygen due to it already being mostly saturated with it.
Also the bottom left is supposed to be cells respiring very heavily, so what is the steep bit in the middle? Cells respiring progressively less heavily??


Thanks for reading ik it’s quite long but as I said I’m rlly confused lol so any help would be appreciated!

Here’s a pic of one:Name:  AE6B3D4D-C41E-41AB-B7B5-128BD1DB8311.jpeg
Views: 9
Size:  162.1 KB
Deoxygenated haemoglobin has a relatively low affinity for oxygen, this is why the curve is flatter nearer the bottom. When one oxygen molecule binds to one haem group, it causes the rest of the haemoglobin to change shape, increasing the affinity of the other haem groups for oxygen, allowing them to bind more easily. This is known as cooperativity. The curve flattens out at the top right because there is only one site available for oxygen to bind.

A right shift means that haemoglobin has reduced affinity for oxygen. Think about it, if the curve shifts to the right, the pO2 has to be higher to achieve the same saturation OR another way to look at it is for a given pO2, haemoglobin has a lower saturation. Carbon dioxide can cause the curve to shift to the right, this is known as the Bohr shift. This is because carbon dioxide bonds to haemoglobin to form carbaminohaemoglobin which has a lower affinity for oxygen. CO2 also shifts the equilibrium (H2O + CO2 <==> H+ + HCO3-) in RBCs to the right. The H+ combines with haemoglobin to form haemoglobinic acid. The H+ ions displaces O2, again lower the affinity of haemoglobin for oxygen.
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