1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 11 Cell Communication

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell-to-Cell Communication Cell-to-cell communication is absolutely essential for multicellular organisms Biologists have discovered some universal mechanisms of cellular regulation Viagra (multicolored) is bound to an enzyme (purple) in a signaling pathway

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings External signals are converted into responses within the cell

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Signal Transduction Pathways – Convert signals on a cell’s surface into cellular responses – Are similar in microbes and mammals, suggesting an early origin

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Local and Long-Distance Signaling Cells in a multicellular organism – Communicate via chemical messengers

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Communication by Direct Contact Between Cells

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 11.3 (b) Cell-cell recognition. Two cells in an animal may communicate by interaction between molecules protruding from their surfaces. In local signaling, animal cells may communicate via direct contact

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Local and long-distance cell communication in animals

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview of Cell Signaling

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reception: A signal molecule binds to a receptor protein, causing it to change shape

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The binding between signal molecule (ligand) and receptor is highly specific A conformational change in a receptor is often the initial transduction of the signal

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intracellular receptors are cytoplasmic or nuclear proteins Signal molecules that are small or hydrophobic can readily cross the plasma membrane use these receptors

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Steroid hormone interacting with an intracellular receptor

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Receptors in the Plasma Membrane There are three main types of membrane receptors: – G-protein-linked – Tyrosine kinases – Ion channel

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure of a G-Protein-Linked Receptor

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Functioning of a G-protein-Linked Receptor

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Structure and Function of a Tyrosine-Kinase Receptor

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A Ligand-Gated Ion-Channel Receptor

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transduction : Cascades of molecular interactions relay signals from receptors to target molecules in the cell Multistep pathways can amplify a signal and provide more opportunities for coordination and regulation

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Signal Transduction Pathways At each step in a pathway the signal is transduced into a different form, commonly a conformational change in a protein

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protein Phosphorylation and Dephosphorylation Many signal pathways include phosphorylation cascades In this process a series of protein kinases add a phosphate to the next one in line, activating it – Phosphatase enzymes then remove the phosphates

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A Phosphorylation Cascade

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Small Molecules and Ions as Second Messengers Second messengers are small, nonprotein, water-soluble molecules or ions Cyclic AMP (cAMP) -made from ATP

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings cAMP as a Second Messenger

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Calcium ions and Inositol Triphosphate (IP 3 ) Calcium, when released into the cytosol of a cell, acts as a second messenger in many different pathways

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The maintenance of calcium ion concentrations in an animal cell

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Other second messengers such as inositol triphosphate (IP3) and diacylglycerol (DAG) can trigger an increase in calcium in the cytosol

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Calcium and Inositol Triphosphate in Signaling Pathways

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Response: Cell signaling leads to regulation of cytoplasmic activities or transcription

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cytoplasmic response to a signal: the stimulation of glycogen breakdown by epinephrine

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nuclear response to a signal: the activation of a specific gene by a growth factor

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fine-Tuning of the Response Signal pathways with multiple steps can amplify the signal and contribute to the specificity of the response

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Signal Amplification Each protein in a signaling pathway amplifies the signal by activating multiple copies of the next component in the pathway

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Specificity of Cell Signaling The different combinations of proteins in a cell give the cell great specificity in both the signals it detects and the responses it carries out

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Specificity of Cell Signaling

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Scaffolding Proteins Increase Transduction Efficiency

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Termination of the Signal Signal response is terminated quickly by the reversal of ligand binding