Methemoglobin question

[dragon72]

question: why the conversion from normal hemoglobin to methemoglobin causes the dissociation curve to shift left instead of right. If it shift left then affinity for oxygen would increase and that is wrong. I don 't understand why.

Thanks in advance,
Andy

 

[IndDent]

where is this question from? If your talking about myoglobin -stuff found in muscle- then yes myoglobin is to the left of hemoglobin on the oxygen dissociation curve. Meaning, that myoglobin has a higher affinity for oxygen than hemoglobin. So when hemoglobin comes into the areas of the muscle, it transfers oxygen to myoglobin.

Hope that helps. I've never heard of nor seen methemoglobin before.

 

[rpkall]

I think when one heme (of one of the chains) is in an Fe3+ state, the molecule "acts" as if that heme is oxygenated (exhibiting cooperativity; even though there's really no O2 there)--and this increases the affinity of that hemoglobin molecule for oxygen in the other three binding sites. The curve shifts to the left, and because the molecules have such a high affinity for oxygen, unloading to tissues is impaired.

I think. ahahaha