Chapter Objectives

1. Categorize chemical signals in terms of the proximity of the communication cells
2. Overview the basic elements of a signaling system of a target cell
3. Describe the nature of a ligand-receptor interaction and state how such interactions initiate a signal transduction system
4. Compare and contrast G-protein-linked receptors, tyrosine-kinase receptors, and ligand-gated ion channels
5. Describe how phosphorylation propagates signal information
6. Describe how cyclic adenosine monophosphate (cAMP) is formed and how it propagates signal information
7. Describe how the cytoplasmic concentration of Ca²⁺ can be altered and how this increased pool of Ca²⁺ is involved with signal transduction
8. Describe how signal information is transduced into cellular responses in the cytoplasm and in the nucleus
9. Describe how signla amplification is accomplished in target cells
10. Describe how target cells discriminate among signals nad how the same signal can elicit multiple cellular responses

Chapter Terms:

Chapter Outline Framework

1. An Overview of Cell Signaling
   1. Cell signaling evolved early in the history of life
   2. Communicating cells may be close together or far apart
   3. The 3 stages of cell signaling
      1. Reception
      2. Transduction
      3. Response
2. Signal Reception and the Initiation of Transduction
   1. A chemical signal binds to a receptor protein, causing the protein to change shape
   2. Most signal receptors are plasma-membrane proteins
3. Signal Transduction Pathways
   1. pathways relay signals from receptors to cellular responses
   2. Protein phosphorylation, a common mode of regulation in cells, is a major mechanism of signal transduction
   3. Certain small molecules and ions are key components of signaling pathways (2nd messengers)
4. Cellular Responses to Signals
   1. In response to a signal, a cell may regulatae activities in the cytoplasm or transcription in the nucleus
   2. Elaborate pathways amplify and specify the cell's responses to signal

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