Chapter 11 - In-Class Presentation

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  • 1. Chapter 11:Cell Communication
  • 2.
    • 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)
    • 3. These communications are deliberately initiated, received, and interpreted in order to increase the physiological coordination of the cells in multicellular organisms
    • 4. We will consider in particular those events that follow the reception of a chemical signal
    • 5. We will not dwell on the purpose of the signal
    • 6. We also will not dwell on why and how a given cell releases a given signal
    Signal-Transduction Emphasis
  • 7. Signaling with Direct Contact
  • 8. Local Signaling w/o Direct Contact
    e.g., interferon release by viral-infected cells
  • 9. Long-Distance Signaling
  • 10. Note how specificity is determined by presence/absence of receptor protein
    Long-Distance Diffusion
  • 11. Signalling, Free-Living Cells
  • 12.
    • Three general categories of chemical signaling:
    • 13. Cytoplasmic connections between cells
    • 14. Cell-to-cell contact-mediated signaling
    • 15. Free diffusion between cells
    • 16. Distant cells (hormones)
    • 17. Adjacent cells (within interstitial space)
    • 18. All of latter involves the physical movement of ligands
    • 19. That is, ligand reception by a protein
    • 20. Note that reception means molecule-to-molecule contact
    Cell-Cell Chemical Signaling
  • 21. e.g., nitric oxide
    e.g., steroid hormones
    Ligands
    Nothing to memorize on this page
    e.g., insulin
    e.g., epinephrine
  • 22. Signal Transduction
    Often turning on or off enzyme activity
    In this case the receptor protein is a membrane protein
    Ligand
  • 23. 1. Reception
    3. Response
    2a. Transduction
    Three Stages
    2b. Transduction
    2c. Transduction
    2d. Transduction
    Responses usually involve increasing or decreasing some protein’s function
  • 24. 1. Reception
    Three Stages
    2a. Transduction
    2b. Transduction
    3. Response
  • 25. Intracellular Receptor
  • 26. Slower response if requiring protein synthesis
    Rapidity of Response
  • 27. G-Protein-Linked Receptor
    G proteins bind GTP
  • 28. G-Protein-Linked Receptor
    The more ligand binding, the greater the cellular response
    Note lability of all signals
  • 29. Protein Kinase & Phosphatase
    Therefore, responses tend to continue (or expand) only so long as signaling continues
    This reversibility contributes to the dynamic nature of cells
    Like signal lability, reversibility of phosphorylation makes signaling reversible
  • 30. Tyrosine Kinase Receptor
  • 31. Receptor Tyrosine Kinase
    Note steps involved:
    Ligand Reception
    Receptor Dimerization
    Catalysis (Phosphorylization)
    Subsequent Protein Activation
    Further Transduction
    Response
  • 32. Reversibility is assured by pumping ions back out again (using separate protein)
    Ion-Channel Receptor
  • 33. Phosphorylation Cascade
  • 34. Cyclic AMP (cAMP)
    Note reversibility
    “Second” Messenger
    Second messengers are not proteins
  • 35. 2nd Messenger, S.T.P.
  • 36. Releasing Ca2+ is a means of greatly amplifying signal
    Ca2+-mediated Signal Amp.
  • 37. Signal Amplification (Cascade)
  • 38. Note how, via catalysis, one ligand molecule binding gives rise to many new intracellullar molecules
    Signal Amplification (Cascade)
  • 39. Signal Amplification (Cascade)
  • 40. Signal-Transduction Cascade
    Seek to understand the concept, rather than memorize the specific protein
  • 41. Nuclear Response
  • 42. Note that more than one response can result from the reception of a single ligand
    Various Responses
  • 43.
    • Same ligand gives rise to different responses
    • 44. (here same receptor, different relay)
    • 45. Cells differ in terms of their proteins
    • 46. Different proteins respond differently to the same environmental signals
    Various Responses
  • 47. The End