Cell communication and the cell cycle flashcards

Cell communication allows cells to detect and respond to signals from their environment and from other cells. Signals bind to receptors, triggering a cascade of molecular events that ultimately change cell behavior. Students must understand the three stages of cell signaling: reception, transduction, and response. Signal transduction often involves second messengers and protein phosphorylation. The cell cycle describes the ordered series of events by which a cell grows and divides, including interphase (G1, S, and G2) and mitotic phase. Checkpoints controlled by cyclins and cyclin-dependent kinases (CDKs) ensure the cycle proceeds correctly. Apoptosis is a regulated form of cell death tied to signaling pathways. Disruption of normal cell cycle control, such as mutations in proto-oncogenes or tumor suppressor genes, can lead to cancer.

1. Card 1

   What are the three stages of cell signaling?

   Reception, transduction, and response. A signal molecule binds a receptor, a cascade converts the signal, and the cell produces a specific response.

2. Card 2

   What is a ligand?

   A ligand is a signaling molecule that binds specifically to a receptor, triggering a conformational change that initiates a cellular response.

3. Card 3

   How do G-protein-coupled receptors (GPCRs) work?

   A ligand binds the receptor, activating a G-protein, which then activates an effector enzyme like adenylyl cyclase, producing second messengers such as cAMP.

4. Card 4

   What role does cAMP play in signal transduction?

   cAMP is a second messenger produced from ATP by adenylyl cyclase. It activates protein kinase A, amplifying the signal and altering cell activity.

5. Card 5

   What is phosphorylation and why is it important in signaling?

   Phosphorylation is the addition of a phosphate group to a protein by a kinase. It activates or deactivates proteins, relaying and amplifying signals in a cascade.

6. Card 6

   What happens at each checkpoint of the cell cycle?

   Checkpoints at G1, G2, and the M phase verify that DNA is undamaged and conditions are favorable before allowing the cycle to proceed to the next stage.

7. Card 7

   What are cyclins and CDKs?

   Cyclins are regulatory proteins whose levels fluctuate; they bind and activate cyclin-dependent kinases (CDKs), which phosphorylate target proteins to drive cell cycle progression.

8. Card 8

   What is the difference between a proto-oncogene and an oncogene?

   A proto-oncogene normally promotes controlled cell division. A mutation converts it into an oncogene, causing excessive cell proliferation and potentially cancer.

9. Card 9

   What is the function of tumor suppressor genes?

   Tumor suppressor genes encode proteins like p53 that slow or stop the cell cycle, repair DNA, or trigger apoptosis, preventing uncontrolled cell growth.

10. Card 10

    What is apoptosis and what triggers it?

    Apoptosis is programmed cell death. It is triggered by internal signals like DNA damage or external death signals, and involves caspase activation and cell self-destruction.

11. Card 11

    How does paracrine signaling differ from endocrine signaling?

    Paracrine signaling acts locally on nearby cells, while endocrine signaling uses hormones released into the bloodstream to reach distant target cells.

12. Card 12

    What occurs during the S phase of interphase?

    During S phase (synthesis phase), the cell replicates its entire DNA, producing two identical sister chromatids joined at the centromere for each chromosome.

• Many students confuse the S phase with mitosis, forgetting that DNA replication occurs during interphase, not during the mitotic phase of the cell cycle.
• Students often think a single mutation in a proto-oncogene or tumor suppressor gene is sufficient to cause cancer, when in reality multiple mutations in several regulatory genes are typically required.
• A common error is assuming that signal molecules enter the cell to cause a response, when most hydrophilic ligands bind surface receptors and never cross the plasma membrane.

Planning your revision? Read how to revise AP Biology, or make cards from your own notes with the notes to flashcards tool.