Guiding Questions
An Overview of Cell Signaling
- Describe the basic signal-transduction pathway used for mating in yeast. Explain why we believe these pathways evolved before the first multicellular organisms appeared on Earth.
- Define paracrine signaling and give an example.
- Define local regulation and explain why hormones are not local regulators.
- Explain how plant and animal hormones travel to target cells.
- List and briefly define the three stages of cell signaling.
Signal Reception and the Initiation of Transduction
- Describe the nature of a ligand-receptor interaction and state how such interactions initiate a signal-transduction system.
- State where signal receptors may be located in target cells.
- Compare and contrast G-protein-linked receptors, tyrosine-kinase receptors, and ligand-gated ion channels.
Signal-Transduction Pathways
- Describe two advantages of using a multistep pathway in the transduction stage of cell signaling.
- Explain how the original signal molecule can produce a cellular response when it may not even enter the target cell.
- Describe how phosphorylation propagates signal information.
- Explain why a single cell may require hundreds of different protein kinases.
- Explain how protein phosphatases turn off signal-transduction pathways.
- Define the term second messenger. Briefly describe the role of these molecules in signaling pathways.
- Describe how cyclic AMP is formed and how it propagates signal information in target cells.
- Explain how the cholera bacterium causes the symptoms of cholera by disrupting G-protein-signaling pathways.
- Describe how the cytosolic concentration of Ca2+ can be altered and how the increased pool of Ca2+ is involved with signal transduction.
Cellular Responses to Signals
- Describe how signal information is transduced into cellular responses in the cytoplasm and in the nucleus.
- Describe how signal amplification is accomplished in target cells.
- Explain why different types of cells may respond differently to the same signal molecule.
- Explain how scaffolding proteins help to coordinate a cell’s response to incoming signals.
