I suspect that the authors of the papers I have alluded to don't fully understand either, which is why there are differences. Certainly when I have mentioned it here at work, the others in the lab who are also working with iron just look at me blankly! I understand about the loss/gain of electrons (Fe2+ is oxidised, so looses an electron and becomes Fe3+), and that this process can be measured (hence the numbers and mV) but how come the numbers are so different? (rhetorical question!)
At the moment I'll just leave it as 'redox potential makes iron very versatile'
i don't know where the numbers have come from, but you presumably have that information. what the words and the second & third ranges indicate are that in different chemical environments, which of the ferrous (Fe 2+) and ferric (Fe 3+) ions is the lower energy state varies - and that it's possible that under certain conditions, they may be of equal energy.
this is iirc the key property that enables haemoglobin to both pick up, and to drop off, oxygen. if either the ferric ion, or the ferrous ion, were always (& by great enough a margin) the higher energy state of the two, this would not occur - and we, along with all animals on earth (except copper-based oxidising agent transport mechanism oddities, and things that live in a reducing environment) wouldn't exist.
does this make better - and appropriate - sense ?
i suspect the wildly different first range figure comes from having taken a different zero point from the other two, whose ranges are approximately 900 mV, whilst it gives a range of 1200 mV: but i don't know how whoever did
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I understand about the loss/gain of electrons (Fe2+ is oxidised, so looses an electron and becomes Fe3+), and that this process can be measured (hence the numbers and mV) but how come the numbers are so different? (rhetorical question!)
At the moment I'll just leave it as 'redox potential makes iron very versatile'
Reply
this is iirc the key property that enables haemoglobin to both pick up, and to drop off, oxygen. if either the ferric ion, or the ferrous ion, were always (& by great enough a margin) the higher energy state of the two, this would not occur - and we, along with all animals on earth (except copper-based oxidising agent transport mechanism oddities, and things that live in a reducing environment) wouldn't exist.
does this make better - and appropriate - sense ?
i suspect the wildly different first range figure comes from having taken a different zero point from the other two, whose ranges are approximately 900 mV, whilst it gives a range of 1200 mV: but i don't know how whoever did ( ... )
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