Oxygene entry into cells
francis.durst at bota-ulp.u-strasbg.fr
Fri Feb 20 13:05:45 EST 1998
In article <01bd3d4b$40eda6c0$df80808f at bchm7.bch.unp.ac.za> "che" <pillayc at biochem.unp.ac.za> writes:
>From: "che" <pillayc at biochem.unp.ac.za>
>Subject: Oxygene entry into cells
>Date: 19 Feb 1998 15:28:47 GMT
>Whilst I know that oxygen is delivered to cells by haemoglobin, how does
>this oxgen enter the cells ? Is this oxygen chanelled to the mitochondria
>by intracellular carrier molecules ? Why does this oxygen not react with
>cellular reducing agents (like glutathione) which are present at high
>concentrations in the cytoplasm. Oxygen (O2) is a non-polar molecule, why
>should it dissolve into the cytoplasmic mileu when it could easily dissolve
>into the lipid bilayer ? If this is the case, would there not be a chance
>of fatty acid oxidation ?
>Any references would be greatly appreciated.
I think the reaction of O2 with organic molecules is spin-hindred: O2 is
triplet while most organics are singlet, this is basically why, although we
are made of mostly reduced organic matter, we do not burst in flames (even at
spring time when the activation energy of the younger ones is at peak
level!). In a poetic way (the 'real' chemists will balk) you may envisaged
it as follows:O2 is a diradical with two electrons with parallel spin, so for
it to insert in say a C-H bond, one spin has to reverse, which takes more time
than the rapid contact when O2 bounces into an organic molecule. So the
reaction is kinetically unfavored, but of course occurs at a low rate (butter
becoming rancid etc...).
To react, O2 has to be activated, which is what all oxygenases (and
hemoglobin) do, by binding to a transition metal, or as a flavin
And O2 IS soluble at a few ppm (depending on temp) in water and cytoplasm
which is well enough to diffuse to the reaction centers.
All the best
Francis Durst, IBMP
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