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What is the final stage of aerobic catabolism of carbohydrates ?

Discussion in 'MCAT Study Question Q&A' started by SaCkO, 04.23.12.

  1. SaCkO

    SaCkO

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    What is the final stage of aerobic catabolism of Carbohydrates?
    Kreb's cycle?
    Oxidative phosphorylation?

















    On BR CBT 5.. One of the answer choices choices that is said to be correct according to BR that the final stage of aerobic catabolism is Kreb's Cycle.
    I thought that it is oxidative phosphorylation so i picked it as the false answer.

    this is what they explained in answer choice
    Pyruvate is the end product of glycolysis under aerobic conditions. Glycolysis involves the oxidation of carbohydrates like glucose. Thus, choice A is a true statement. In the first paragraph of the passage, we find that the Krebs cycle is also the final common pathway for the oxidation of amino acids. It would seem likely that if some of the intermediates of the Krebs cycle were to be removed (and some are), they could be converted into amino acids.[/COLOR]

    Is BR wrong and they worded the question in a wrong way? or Iam I missing something here ? Can somebody share wt they would answer that question if they were in the same situation?
  2. kasho11

    kasho11

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    I think they're saying that the final stage of carbohydrate metabolism is the Kreb's cycle because that is when you completely break down the original glucose molecule into energy carriers and CO2. The CO2 gets excreted and the energy carriers go on to perform oxidative phosphorylation in the electron transport chain.

    It is a convoluted question and I don't think it would be asked that way on the MCAT.
  3. loveoforganic

    loveoforganic -Account Deactivated-

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    TCA for sure. The reducing equivalents going into the ETC have no shared atoms with carbohydrates (well, they may have a hydrogen, but that hydrogen isn't undergoing oxidation or reduction)
  4. MedPR

    MedPR

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    This. The ETC does not itself breakdown (catabolize) anything, it just transports electrons (electron transport chain)!!

    I agree that it's a little convoluted, but I think it's a valid question (especially considering this is TBR) to trick people who are just grouping related concepts together and not really grasping what they are.
  5. SaCkO

    SaCkO

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    Well if you look at it from the way you are presenting it then Kreb's cycle is not catabolizing anything
    it is just moving electrons around too through hydrogen
    What if the question was asking what is the final stage of anaerobic catabolism of glucose, then you cannot say that it is glycolysis because it is fermentation because you need to regenerate the NADH+

    The only way to finish the catabolism process of glucose in aerobic conditions is to regenerate the NADH+ and FADH2 so I find that ETC is a more viable answer
    Did I make any sense?
  6. loveoforganic

    loveoforganic -Account Deactivated-

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    What happened to all those C-C bonds in glucose? They got broken (catabolism). Where is that happening in the ETC?
  7. pfaction

    pfaction

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    I was going to say that O2 got catabolized at the end of ETC, but technically, isn't H2O anabolism?
  8. loveoforganic

    loveoforganic -Account Deactivated-

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    I would say glycolysis, although it isn't quite as clear because you have lactate dehydrogenase breaking a C=O bond
  9. loveoforganic

    loveoforganic -Account Deactivated-

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    Yes, but that O2 doesn't have anything to do with the glucose molecule anyway
  10. pfaction

    pfaction

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    How can it be glycolysis when PDC breaks down pyruvate into acetyl (or whatever it is)

    Also good point on the O2 part.
  11. loveoforganic

    loveoforganic -Account Deactivated-

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    Lactate dehydrogenase complex, not PDC, is pyruvate <--> lactate

    PDC is only going to catalyze under aerobic conditions (well, it'll do anaerobic for a bit but quickly be shut down due to negative feedback).
  12. SaCkO

    SaCkO

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    Well you are refering to catabolism as C-C bonds which is wrong because there are hydrogen too in a carbohydrate and these hydrogens are still moved untill the ETC where they rest at water as the end product ..
    And the answer for that during anaerobic respiration is definitely fermentation.
    please refer to this file.

    http://www.sci.uidaho.edu/biosci/lecture/Stenkamp/121/topics 6 and 7.pdf
    ..
    I like BR however guys we shouldn't just follow the general flow if something is not writen right. And as kasho said it is a convoluted question and not MCAT type.

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