Home / Flashcard library / Health & emergency services / MCAT / Cell & Molecular

Health & emergency services

MCAT Biology — Cell & Molecular flashcards

10 of 60 cards free to study here · 11 topics · the whole deck is built into Willys

DNA replication, transcription and RNA processing, translation, gene regulation, mutations and repair, the cell cycle and meiosis, membranes and transport, organelles, signaling, viruses and prokaryotes, and the recombinant DNA toolkit.

Get the app All MCAT decks

Learn deck · part of MCAT · written against: AAMC MCAT content outline (2015 exam, current through 2026). Updated 2026-10-10.

Study the free sample

10 cards from the deck as they are. Flip, rate yourself, filter by topic; your progress stays in this browser.

The 10 sample cards as a list
  1. Which DNA base pair is held together by three hydrogen bonds, and what does that mean for melting temperature?
    Guanine–cytosine pairs have three hydrogen bonds; adenine–thymine pairs have only two. DNA rich in G–C therefore needs a higher temperature to separate its strands (G–C pairs also stack more strongly with their neighbors, which adds to the effect), which matters when designing PCR primers.
    DNA Structure & Replication
  2. How does RNA polymerase differ from DNA polymerase in what it needs to start, and which DNA strand does it read?
    RNA polymerase needs no primer and has little proofreading ability. It reads the template (antisense) strand 3' to 5' while building RNA 5' to 3', so the transcript matches the coding (sense) strand except that uracil replaces thymine.
    Transcription & RNA Processing
  3. What does it mean that the genetic code is degenerate but unambiguous?
    Degenerate: most amino acids are specified by more than one codon (61 sense codons for 20 amino acids).

    Unambiguous: any given codon always means the same amino acid. The code is also read in non-overlapping triplets and is nearly universal, with AUG serving as the start codon for methionine.
    Translation
  4. How does the lac operon stay off when lactose is absent, and how is it turned on?
    The lac repressor sits on the operator and blocks RNA polymerase. When lactose is present, its isomer allolactose binds the repressor, which changes shape and falls off, letting the structural genes (including β-galactosidase and lactose permease) be transcribed; this makes the operon inducible.
    Gene Regulation
  5. What is the difference between a missense and a nonsense mutation?
    A missense mutation changes one codon so it specifies a different amino acid, with effects ranging from none to severe depending on how different the new residue is. A nonsense mutation changes a codon into a stop codon, truncating the protein, which is usually far more damaging. A silent mutation changes the codon but not the amino acid.
    Mutations & DNA Repair
  6. How does cholesterol affect membrane fluidity?
    It is a fluidity buffer: at high temperatures its rigid rings restrain phospholipid movement, while at low temperatures it wedges between the tails and stops them packing into a solid. The result is a membrane that stays suitably fluid across a wider range of temperatures.
    Membranes & Transport
  7. How do the rough and smooth endoplasmic reticulum differ in function?
    The rough ER is studded with ribosomes making proteins destined for secretion, the membrane or the lysosome; a signal sequence on the growing chain is what docks the ribosome there. The smooth ER has no ribosomes and makes lipids and steroids, detoxifies drugs and stores calcium (as the sarcoplasmic reticulum in muscle).
    Organelles
  8. What happens inside the cell when a ligand activates a G protein-coupled receptor?
    The receptor makes its G protein swap GDP for GTP, and the activated α subunit then acts on an effector: Gs stimulates adenylyl cyclase to make cAMP (activating protein kinase A), Gi inhibits it, and Gq activates phospholipase C to release IP₃ and DAG, raising intracellular calcium. The α subunit's own GTPase activity switches the signal off.
    Cell Signaling
  9. Which features distinguish a prokaryotic cell from a eukaryotic cell?
    Prokaryotes have no nucleus or membrane-bound organelles, typically a single circular chromosome in a nucleoid, smaller 70S ribosomes (versus 80S in eukaryotes), usually a peptidoglycan cell wall, and they divide by binary fission. The ribosome difference is what lets many antibiotics hit bacteria but not us.
    Viruses & Prokaryotes
  10. What does a PCR reaction contain, and what happens in each of its three temperature steps?
    Template DNA, two primers flanking the target, a heat-stable Taq polymerase, and dNTPs. Each cycle denatures the DNA near 95 °C, anneals the primers at a lower temperature, and extends them at about 72 °C, doubling the target so that 30 cycles yield about a billion copies.

    Why: Taq comes from a hot-spring bacterium and survives the denaturation step.
    Recombinant DNA Techniques

Unlock the whole deck

You are studying a free 10-card sample. All 60 cards of MCAT Biology — Cell & Molecular, the other 8 MCAT decks, and spaced-repetition scheduling are built into Willys. 14-day free trial, then $14.99 a year.

Get the app

In Willys, tap Exam Library at the top of your Decks (or Browse Exam Library… under the + button), find the exam on its shelf or by search, tick it and tap Add.

More MCAT decks

Amino Acids & ProteinsQuick Drills: Amino AcidsEnzymes & KineticsMetabolismCloze: Enzymes & RegulatorsPractice Questions, Part 1: BiochemistryHigh-Yield Terms & TheoristsPractice Questions, Part 2: Biology & Psych/Soc

← All MCAT decks, with the study guide and topic outline.

About these cards

Review status: Second-reader reviewed, with corrections applied.

Checked against:

  • OpenStax Biology 2e and OpenStax Microbiology, consulted as references; no text copied.
  • Facts cross-checked against Alberts et al., Molecular Biology of the Cell, 7th ed. (reference only; no text copied).

These are independent study notes written for Willys. They are not official exam material, may contain mistakes, and are no substitute for your course, your teacher or the exam owner's own publications. Found an error? Tell us — corrections ship as a new version of the deck.

Not clinical guidance. These cards prepare you for an exam. Never use them to make decisions about a patient's care: follow current guidelines, prescribing information and your institution's policies. The decks contain no doses.

MCAT® is a registered trademark of the Association of American Medical Colleges (AAMC), which is not affiliated with and does not endorse this product.

Use of these pages is covered by our Terms of Use.