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Microbiology Flashcards

7 cards from real PCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Microbiology flashcards as text

  1. Which bacterium uses a type III secretion system to inject effector proteins directly into host cell cytoplasm?

    Answer: Salmonella enterica

    Salmonella uses its type III secretion system (injectisome) to deliver effector proteins into epithelial cells, triggering actin rearrangement and bacterial uptake.

  2. In a continuous culture system (chemostat), bacterial growth rate is controlled by:

    Answer: Dilution rate of limiting nutrient

    In a chemostat, the dilution rate determines the growth rate because the limiting nutrient is supplied at a fixed rate, maintaining steady-state culture conditions.

  3. Which characteristic distinguishes a temperate bacteriophage from a lytic bacteriophage?

    Answer: Ability to integrate into the host chromosome as a prophage

    Temperate phages can integrate their DNA into the bacterial chromosome (becoming a prophage) and remain dormant, while lytic phages always lyse the host immediately.

  4. Clostridium botulinum toxin causes flaccid paralysis by:

    Answer: Cleaving SNARE proteins to prevent acetylcholine release

    Botulinum toxin is a zinc-dependent protease that cleaves SNARE proteins (SNAP-25, synaptobrevin, syntaxin), preventing vesicle fusion and acetylcholine release.

  5. Which Plasmodium species can form hypnozoites in the liver, enabling relapse months after initial infection?

    Answer: Plasmodium vivax

    P. vivax (and P. ovale) form dormant hypnozoites in hepatocytes; primaquine is required to eliminate them and prevent relapse.

  6. Which type of bacterial toxin requires endocytosis and intracellular processing to exert its effect on the host cell?

    Answer: A-B toxin

    A-B toxins consist of a binding (B) subunit that facilitates endocytosis and an active (A) subunit that exerts enzymatic activity intracellularly after processing.

  7. Resistance to beta-lactam antibiotics via production of beta-lactamase enzymes can be overcome by administering:

    Answer: Clavulanic acid

    Clavulanic acid is a beta-lactamase inhibitor that irreversibly binds and inactivates beta-lactamase, protecting co-administered beta-lactam antibiotics.