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the electron transport chain only has 3 spots where nadh, fadh2, and gtp can feed its electrons. each of those 3 spots (on the electron transport chain) makes one atp. nadh2 is fed to the first protien, therefore it goes through all 3 making 3 atp's. fadh2 skips the first protien, and deposits its electrons to the second protien, therefore, fadh2's electrons only go through 2 of the protiens, yielding 2 atp. gtp is feeds its electrons to the third, making only one atp...... remember, nadh2 only makes 3 atp per nadhs when it is making atp via oxidative phosphorylation, in substrate level phos, it makes only 2.
Yes, I think marathons are cool too. Thx for the answer, man!
Fellow marathon addict
More specfically, FADH2 doesn't create 3 ATP because its redox potential is only slightly lower than the complex in the ETC where the electrons from FADH2 enters (Complex II).
Remember that the complexes in the ETC go from more negative to more positive Redox potential as you move further down the line. This change in redox potential is why the ETC can generate an H+ gradient for ATP.
So the electrons from NADH travel from NADH --> I --> III --> IV, which is three increases in redox potential (from NADH to I, then I to III, and III to IV)so 3 ATP are created. (This is very simplified to make it MCAT relevant).
The electrons from FADH2, however, Go from FADH --> Complex II --> Complex III --> Complex IV. In this progression there are only 2 increases in redox potential (from II to III, and III to IV). The change in redox potential between FADH2 and Complex II isn't large enough to translocate H+ to the IMS. Thus, there are only 2 ATP produced.
This isn't advanced biochemistry. I learned this in AP Biology. Biochemistry involved the actual electron transfer mechanisms in each of the complexes and how each product is specifically made.This is pretty funny. They claim you only need basic science for the MCAT and you guys are worried about material I just went over in a 3rd year biochem class.
I think the AAMC needs to work on its honesty level a bit with what test takers need to cover.