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Unformatted text preview: on donor than B, and B must be a better electron acceptor than A. And since it
is a spontaneous reaction, ÄG < 0. Thus, such a transfer of electrons is an energy-yielding
reaction and the amount of free energy released depends the magnitude of the difference in
electron affinity between molecule A and molecule B. The magnitude is quantified in volts,
and designated as ÄEo.
[We can calculate the Gibbs free energy change for an electron transfer in a manner similar to
how we did it for a chemical reaction: ÄG = nF(ÄEo), where n is the number of electrons
transferred in the exchange and F is the Faraday constant (100 kJ/Vmole).
So, for example, in the transfer of a pair (2) of electrons from NADH to O2, the ÄEo is 1.14V,
so the energy change is:
ÄG = nF(ÄEo) = (2)(100 kJ/Vmole)(1.14 V) = 228 kJ/mole ]
<Thus, the reaction (passing a pair of electrons from NADH to O2 to form H2O) is highly
energetically favorable and thus spontaneous. This large free energy difference can be harnessed to do
useful work. In the mitochondrion this energy will be used to pump protons out of the matrix and into
the intermembrane space....> III. “Oxidative Phosphorylation” – electron transport and mitochondrial ATP synthesis
(A) Electron transport: using the energy of e transfer to create a H+ gradient across the
IMM (see fig below or 14-9 in ECB; DVD 14-2)
(1) The inner mitochondrial membrane (IMM) is rich in a set of molecules (mostly
proteins) that can accept electrons from molecules with lower electron af...
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- Fall '10
- cell biology