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AP Biology: Cell Communication and the Cell Cycle — quiz

10 multiple-choice questions covering Overview of Cell Signaling, Cell-to-Cell Communication Types, Receptors, Second Messengers, Phosphorylation Cascades. One answer each; you get a score at the end and the explanation for every question. No account needed.

Updated 2026-11-03. Keys 1–4 pick an answer, Enter moves on. Redo it any time, in order or shuffled.

The questions

Answers and explanations are shown after you finish.

1. Overview of Cell Signaling

   A target cell's receptor binds epinephrine, which sets off a chain of molecular events inside the cell before glycogen breakdown begins. Which stage of the signal transduction pathway includes this internal chain of events?

   • Response
   • Reception
   • Transduction
   • Amplification
2. Cell-to-Cell Communication Types

   During wound healing, a skin cell releases growth factor proteins that diffuse through the extracellular fluid and bind receptors on several nearby skin cells, causing them to divide. What type of signaling is this?

   • Autocrine signaling
   • Paracrine signaling
   • Synaptic signaling
   • Endocrine signaling
3. Cell-to-Cell Communication Types

   Cardiac muscle cells coordinate their contractions by allowing ions to pass directly from the cytoplasm of one cell to the next through specialized channels, without any molecule being released into the extracellular space. This is best classified as which form of cell communication?

   • Paracrine signaling
   • Direct contact (gap junction) signaling
   • Autocrine signaling
   • Endocrine signaling
4. Receptors

   A receptor activates an associated protein by stimulating the exchange of GDP for GTP, and the activated protein later turns itself off by hydrolyzing that GTP back to GDP. This mechanism describes which receptor type?

   • G-protein-coupled receptor
   • Intracellular receptor
   • Ligand-gated ion channel
   • Receptor tyrosine kinase
5. Receptors

   A membrane receptor must dimerize with an identical receptor after ligand binding, after which both subunits add phosphate groups to each other, creating docking sites for several different relay proteins at once. Overexpression of this receptor type is strongly linked to cancer because...

   • a single activated receptor can simultaneously trigger multiple signaling pathways promoting cell division
   • it directly opens an ion channel causing unregulated calcium influx
   • it binds DNA directly as a transcription factor without any cytoplasmic signaling
   • it only responds to steroid hormones that diffuse freely into the cell
6. Second Messengers

   In liver cells, epinephrine binding its receptor leads to activation of an enzyme that converts ATP into a small second messenger, which then activates protein kinase A to trigger glycogen breakdown. Which enzyme carries out this conversion?

   • Glycogen phosphorylase
   • Adenylyl cyclase
   • Protein kinase C
   • Phospholipase C
7. Second Messengers

   An activated enzyme cleaves a membrane phospholipid into two products: one diffuses to the endoplasmic reticulum to trigger calcium release, and the other stays in the membrane to help activate protein kinase C. Which enzyme produces these two second messengers?

   • Protein kinase A
   • Adenylyl cyclase
   • Phospholipase C
   • Tyrosine kinase
8. Phosphorylation Cascades

   A single hormone molecule binding one receptor ultimately leads to activation of thousands of target enzymes inside the cell. This dramatic amplification is best explained by which feature of the signaling pathway?

   • Each activated kinase in a cascade phosphorylates many downstream molecules before being deactivated by a phosphatase
   • The receptor diffuses throughout the entire cell interacting with every organelle
   • The ligand itself replicates many times inside the cytoplasm
   • The response always directly alters DNA replication rates
9. Feedback Loops

   After eating a meal, rising blood glucose triggers insulin release from the pancreas; as blood glucose falls back toward normal, insulin secretion decreases as well. This regulatory pattern is an example of which type of feedback?

   • Paracrine feedback
   • Negative feedback
   • Positive feedback
   • Autocrine feedback
10. Cell Cycle Phases & Checkpoints

    A cell has just finished replicating its DNA, giving each chromosome two sister chromatids, but has not yet entered mitosis. Which phase of the cell cycle is it currently in?

    • M
    • G1
    • S
    • G2