Anonymous1502
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What I understand so far is that when CO2 levels are high the hemoglobin has a lower affinity for oxygen so it releases more oxygen and when CO2 levels are low hemoglobin has a higher affinity for oxygen so it releases less oxygen.

Can someone explain to me why does this happen and is there more to the Bohr effect?
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macpatgh-Sheldon
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Yes, hopefully I can explain!in [Hb

The reason (you ask why) for the Bohr effect is that it shifts the graph of pO2 (partial pressure of oxygen) on the x axis against %age saturation of haemoglobin [Hb] with O2 on the y axis to the right.

As you will know, this graph has a sigmoid shape, either cos some imaginary creature called God so designed it OR cos it is a miraculous feat of nature and evolution [depending on whether you believe in non-existent contraptions created by man OR the logical, evidence-based scientific principles originally laid down by Darwin).

This sigmoid shape means that at low pO2 (in tissues) a very large amount of O2 is released and at high pO2 (in lungs), a very high amount of O2 is attached to Hb.

When the graph moves to the right [=Bohr effect; same thing happens with high chloride ion levels [try to work out why - bit of chemistry - sciences work together!]], if you look at the two graphs (same axes: normal plot and Bohr effect plot - I shall try and upload pic for u if TSR allows today - TSR is a bit moody like giggling schoolgirls! sorry), you will see that EVEN MORE O2 is released at the tissues (where O2 is low [so towards the left of the graph] and where CO2 is high [which has produced this Bohr shift]) which is of course what you need [there is an oxygen deficit, with me?], cos these e.g,. muscles that are working like mad to do the 54 miles of cycling (have you done the London-Brighton bike ride b4? - join me next year - BUT BE CAREFUL you will need to pull your socks up man! - it is not easy I can assure you! ) are producing more CO2 leading to the Bohr shift yeah?).

Watch this space as I try to upload pic!

Best of luck in remaining exams!
M
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macpatgh-Sheldon
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Name:  Hb4O8 dissociation curve + Bohr shift.jpg
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Look at curve on right cos pH goes down due to:-

CO2 + H2O = H2CO3

H2CO3 ------> H+ + HCO3-

when CO2 is high

Make sense?

Thanks, M
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