jon at magna.com.au (Jonathon Seally) writes:
>What I am interested in knowing is something that I haven't seen actually
>said in any books. In oxidative phosphorylation two electrons from an NADH
>molecule are passed on to the NADH-Q reductase complex and then pass to the
>cytochrome reductase complex and cytochrome oxidase complex via carriers.
>The pair of electrons passing through these three complexes results in
>three H+ ions being pumped across the inner mitochondrial membrane from the
>matrix to the intermembrane space. What I have never seen actually said is
>whether or not it is these three complexes themselves that actually do the
>pumping, functioning as a port, or whether another complex performs this
>function.
TO the best of my knowledge (sorry no refs) the proteins themselves pump
the protons out but no-one really has a clue how it happens.
Also does a substance like rotenone block the pathway by
>preventing the pair of electrons from being transferred from the NADH-Q
>reductase to the coenzyme Q or does it bind one of these two substances
>(which one?) and disable the transfer, or soak up the electrons itself and
>get rid of them somewhere else?
Inhibitors act in different ways. CO will complex with final
complex blocking the entrance of oxygen. Other inhibitors act by
attaching to approriate complexes, or 'sucking up' the oxygen.
BTW DOn't beleive anyhting a book tells you about how many ATP are
produced per Oxygen or per electron. Fact is that a lot of the protons
pumped out actually leak back through the membrane and bypass the ATPase
altogether. (Brand, harper, Taylor (1993) Biochem J 291:739-748) In
fact teh percentage that leak back depends on how fast ATP is being
produced. Probably you end up with about 50-75% of the protons coming
through the ATPase and therfore about 50-75% of the maximum possible ATP
production.
