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Microbiology: Microbial Metabolism Flashcards

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  1. In the Calvin cycle, how many ATP and NADPH molecules are required to fix 3 molecules of CO2 into one molecule of glyceraldehyde-3-phosphate (G3P)?

    Answer: 9 ATP and 6 NADPH

    Fixing 3 CO2 into one G3P requires 9 ATP and 6 NADPH in the Calvin cycle.

  2. Which of the following describes a chemolithotroph that oxidizes ammonia (NH3) to nitrite (NO2⁻)?

    Answer: Nitrosomonas sp.

    Nitrosomonas is a nitrifying chemolithotroph that oxidizes ammonia to nitrite as its energy source.

  3. Coenzyme A (CoA) functions in metabolism primarily by:

    Answer: Activating acyl groups for transfer in anabolic and catabolic reactions

    CoA contains a thiol group that forms high-energy thioester bonds with acyl groups, activating them for metabolic reactions like fatty acid synthesis and the TCA cycle.

  4. What distinguishes the phosphotransferase system (PTS) from other glucose transport systems in bacteria?

    Answer: It phosphorylates glucose during transport using PEP as the phosphate donor

    The PTS uses phosphoenolpyruvate (PEP) as the phosphate donor, simultaneously transporting and phosphorylating glucose to glucose-6-phosphate.

  5. A mutant E. coli strain lacks functional succinate dehydrogenase. Which statement about its metabolism is most accurate?

    Answer: The TCA cycle and Complex II of the ETC will both be non-functional

    Succinate dehydrogenase is shared between the TCA cycle (succinate→fumarate) and the electron transport chain (Complex II), so its loss disrupts both processes.

  6. In sulfate-reducing bacteria, SO4²⁻ serves as the:

    Answer: Terminal electron acceptor in anaerobic respiration

    Sulfate-reducing bacteria like Desulfovibrio use sulfate as the terminal electron acceptor, reducing it to H2S in anaerobic respiration.

  7. Which anaplerotic reaction replenishes oxaloacetate in the TCA cycle when it is used for biosynthesis?

    Answer: Pyruvate + CO2 → oxaloacetate (pyruvate carboxylase)

    Pyruvate carboxylase adds CO2 to pyruvate to regenerate oxaloacetate, replenishing TCA cycle intermediates drained for biosynthesis.