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Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
Chapter 11: Cell Communication
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Chapter 11: Cell Communication

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  • 1. Chapter 11:Cell Communication
  • 2. Signal-Transduction Emphasis  This chapter’s emphasis is on signals that are released from one cell and allowed to freely diffuse to a second (or more) recipient cell(s)  These communications are deliberately initiated, received, and interpreted in order to increase the physiological coordination of the cells in multicellular organisms  We will consider in particular those events that follow the reception of a chemical signal  We will not dwell on the purpose of the signal  We also will not dwell on why and how a given cell releases a given signal
  • 3. Signaling with Direct Contact
  • 4. Local Signaling w/o Direct Contact e.g., interferon release by viral-infected cells
  • 5. Long-Distance Signaling
  • 6. Long-Distance Diffusion Note how specificity is determined by presence/absence of receptor protein
  • 7. Signalling, Free-Living Cells
  • 8. Cell-Cell Chemical Signaling  Three general categories of chemical signaling: • Cytoplasmic connections between cells • Cell-to-cell contact-mediated signaling • Free diffusion between cells •Distant cells (hormones) •Adjacent cells (within interstitial space)  All of latter involves the physical movement of ligands • That is, ligand reception by a protein • Note that reception means molecule-to- molecule contact
  • 9. e.g., nitric oxide e.g., steroid hormonesLigands e.g., insulin Nothing to e.g., epinephrine memorize on this page
  • 10. Signal Transduction Often turning on or off enzyme activity In this case the receptor proteinLigand is a membrane protein
  • 11. Three Stages 1. Reception 2a. Transduction 2b. Transduction 2c. Transduction 2d. Transduction 3. ResponseResponses usually involve increasing or decreasing some protein’s function
  • 12. Three Stages 1. Reception 2a. Transduction 2b. Transduction 3. Response
  • 13. Intracellular Receptor
  • 14. Rapidity of Response Slower response if requiring protein synthesis
  • 15. G-Protein-Linked Receptor bind GTP G proteins
  • 16. G-Protein-Linked ReceptorThe more ligand binding, the greater the cellular response Note lability of all signals
  • 17. Protein Kinase & Phosphatase Protein Kinase O Protein OH + ATP Protein O P O + ADP O Pi H2O Protein Phosphatase Therefore, res Like signal This ponses tend to lability, reversib reversibility continue (or ility of contributes expand) only phosphorylatio to the so long as n makes dynamic signaling signaling nature of continues reversible cells
  • 18. Tyrosine Kinase Receptor
  • 19. Receptor Tyrosine KinaseNote steps involved:1. Ligand Reception2. Receptor Dimerization3. Catalysis (Phosphorylization)4. Subsequent Protein Activation5. Further Transduction6. Response
  • 20. Ion-Channel Receptor Reversibility is assured by pumping ions back out again (using separate protein)
  • 21. Phosphorylation Cascade
  • 22. Cyclic AMP (cAMP) Note reversibility “Second”Messenger Second messengers are not proteins
  • 23. 2nd Messenger, S.T.P.
  • 24. Ca2+-mediated Signal Amp. Releasing Ca2+ is a means of greatly amplifying signal
  • 25. Signal Amplification (Cascade)
  • 26. Signal Amplification (Cascade) Note how, via catalysis, one ligand molecule binding gives rise to many new intracellullar molecules
  • 27. Signal Amplification (Cascade)
  • 28. Signal-Transduction Cascade Seek to understand the concept, rather than memorize the specific protein
  • 29. Nuclear Response
  • 30. Various Responses Note that more than one response can result from the reception of a single ligand
  • 31.  Same ligand gives rise toVarious Responses different responses  (here same receptor, different relay)  Cells differ in terms of their proteins  Different proteins respond differently to the same environmental signals
  • 32. The End

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