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Biology Flashcards

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

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  1. Which enzyme is responsible for removing RNA primers during DNA replication in eukaryotes?

    Answer: RNase H combined with FEN1

    In eukaryotes, RNase H and FEN1 (flap endonuclease 1) work together to remove RNA primers, after which DNA polymerase δ fills the gap.

  2. A cell in G2 phase is treated with a drug that prevents microtubule polymerization. At which checkpoint will cell cycle arrest most likely occur?

    Answer: G2/M checkpoint

    The G2/M checkpoint monitors whether DNA replication is complete and cellular machinery (including microtubules for the spindle) is ready before mitosis begins.

  3. Which type of RNA processing is unique to eukaryotes and involves joining of non-contiguous sequences?

    Answer: RNA splicing

    RNA splicing removes introns and joins exons, creating a mature mRNA from non-contiguous coding sequences—a process absent in prokaryotes.

  4. During which stage of cellular respiration is the most ATP produced per molecule of glucose?

    Answer: Oxidative phosphorylation

    Oxidative phosphorylation generates approximately 32-34 ATP via chemiosmosis driven by the electron transport chain, far exceeding all other stages.

  5. A mutation in which of the following would most directly impair the ability of a eukaryotic cell to target proteins to the endoplasmic reticulum?

    Answer: Signal recognition particle (SRP)

    The signal recognition particle recognizes the signal sequence on nascent polypeptides and directs ribosomes to the ER membrane for cotranslational translocation.

  6. Which of the following correctly describes the Hardy-Weinberg principle?

    Answer: In a large random-mating population without evolutionary forces, allele frequencies remain constant

    Hardy-Weinberg states that in an idealized population (large, random mating, no mutation/migration/selection/drift), allele and genotype frequencies remain constant across generations.

  7. A protein has a Km of 2 mM and a Vmax of 100 μmol/min. At a substrate concentration of 2 mM, what is the reaction velocity?

    Answer: 50 μmol/min

    By the Michaelis-Menten equation, v = Vmax[S]/(Km+[S]) = 100×2/(2+2) = 50 μmol/min; at [S]=Km, velocity is always Vmax/2.