A question about iron oxidation in hemoglobin

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mbmdphd_maybe
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A question about iron oxidation in hemoglobin

Post by mbmdphd_maybe » Mon Nov 07, 2005 6:45 pm

I'm currently taking a physiology course, and we're studying respiratory physiology now and...I must admit, it's made me curious. A good thing, I suppose, considering I want to practice medicine...but that's beside the point.

Here's the thing - the oxygen capacitance curves vary with the partial pressure of CO2 in the blood, with the greatest capacitance being associated with the lowest PaCO2. Now, this to me means that oxygen has the highest affinity for blood (hemoglobin) when blood is at its most basic, and has the lowest affinity for blood when it is at its most acidic.

I know what the reaction of CO2 and water looks like (for anyone who wants to, just ask - I'll reprint it here), and I know that the carbonic anhydrase in the blood leaves a whole bunch of hydrogen ion floating in the blood once the blood reaches the tissue beds, hydrogen ion which complexes with hemoglobin. So...does the acidity or basicity of blood affect the oxidation state of the iron molecule bound to hemoglobin and, if it does, what effect do the different iron oxidation states have on the binding of oxygen?

Anyone who can help would be most appreciated - I've been searching PubMed, BiosisOne, and a number of other services and I haven't been able to find a single paper that addresses exactly what I'm wondering.

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biostudent84
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Post by biostudent84 » Thu Nov 10, 2005 6:17 pm

We actually went over this in my own anatomy class today :)

The lower the acidity (more basic) the blood is, the more oxygen it can hold.

Hemoglobin changes structure as it gains more oxygen molecules. The more oxygen molecules hemoglobin has, the more readily it will accept another oxygen molecule...up to the limit of four oxygen molecules per hemoglobin, or course.

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