NS FL#3 B/B Q2

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  1. nomdeplume1234

    2+ Year Member

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    Question two asks “According to the data in Table 1, how many ATP molecules per carbon result from the oxidative phosphorylation of acetyl-CoA produced during β-oxidation?”

    and according to the passage “Researchers studying the energy yield of fatty acid metabolism estimated the amount of ATP produced in cultured human cells by the β-oxidation of saturated, straight-chain fatty acids of various lengths in both the presence and the absence of oligomycin, an inhibitor of ATP synthase (Table 1)”

    but according to the answer explanation the correct answer is found by assuming that oligomycin blocked ATP synthase. The explanation then goes on to state “the question then asks us how many ATP per carbon result from oxphos”

    but oxphos is never mentioned in the passage.

    Neither the presence of oligomycin nor oxphos are mentioned in the question. Can you explain this question please?
     
  2. ElectricNoogie

    ElectricNoogie MCAT enthusiast

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    Hello! Thanks for your question. This is indeed a challenging Q.

    To begin, the Q does mention and ask us for the ratio of ATP to Carbon from OXPHOS of Acetly CoA, according to the data in table 1. While the passage is not explicit, you should know that the AAMC expects you to recognize the difference between substrate level phosphorylation (glycolysis, Kreb's) and oxidative phosphorlyation (ETC).

    In order to know how many ATP is due to Oxphos, we need to compare the ATP outputs of the cell both with Oxphos and without Oxphos (tx w/ Oligo)

    The 3rd paragraph tells you that Oligomycin acts to directly inhibit ATP synthase.

    Looking at table 1, it doesn't matter which FA you use we simply need to calculate:

    [#ATP made with OxPhos - #ATP made w/o OxPhos (i.e. tx w/ oligomycin] / [# of C in fuel molecule]

    No matter which fuel you choose, you will get 5.5 ATP/C

    Hope this helps, Good Luck!
     

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