What is oxygen's role in the electron transport chain?

1 Answer
Mar 14, 2018

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There are a lot of parts and pieces involved in the electron transport chain, but with respect to Oxygen, the simple answer is Oxygen is the place where the electrons go, it i sthe thing that gets reduced.

I'm not going to link to all the membranes and chemical reactions, but rather just refer to something simple like a carbon in a typical fat.
#-CH_2-# this is what a carbon in a fat looks like (in general).
As that carbon sits now, it has a ~ -2 oxidation state.

When you exhale that carbon as #CO_2# (after cellular respiration and oxidative phosphorylation, etc), the C has a +4 oxidation state.

That means for the Carbon:
#C^-2 = C^"+4" + 6e^-#
Those 6 electrons have to go somewhere. And they go onto Oxygen!
You breath in elemental #O_2# with a zero oxidation number. That carbon above turns into a #CO_2# and basically 1 water, #H_2O#
So that Carbon needs to get rid of 6 electrons...and in #CO_2#, each Oxygen has a -2 oxidation state (from zero to -2), and the water oxygen has a -2 oxidation state (from zero to -2). So when that Carbon in the fat gets oxidized and you breath it out as #CO_2#.
The place were those 6 electrons went is onto the #O_2# that you breathed in (and breathed out as #CO_2# and maybe some water (simplistically speaking)