Chapter 11

1. Chapter 11 Cell Communication

2. 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. External signals are converted into responses within the cell

4. Signal Transduction Pathways • Convert signals on a cell’s surface into cellular responses • Are similar in microbes and mammals, suggesting an early origin

5. Local and Long-Distance Signaling • Cells in a multicellular organism • Communicate via chemical messengers

6. Communication by Direct Contact Between Cells

7. 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. Local and long-distance cell communication in animals

9. Different receptors different cell responses Epinephrine Epinephrine Epinephrine a receptor b receptor b receptor Glycogendeposits Vessel dilates Vessel constricts Glycogen breaks down and glucose is released from cell (a) Intestinal blood vessel (b) Skeletal muscleblood vessel (c) Liver cell Different intracellular proteins different cell responses • The hormone epinephrine • Has multiple effects in mediating the body’s response to short-term stress

10. Overview of Cell Signaling

11. Reception: A signal molecule binds to a receptor protein, causing it to change shape

12. 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

13. Chemical Signaling Mechanisms and Amplification • https://neuroscience5e.sinauer.com/animations07.01.html • http://www.biologyalive.com/life/classes/apbiology/documents/Unit%204/11_Lectures_PPT/media/11_05SignalingOverview_A.swf

14. Intracellular receptors are cytoplasmic or nuclear proteins • Signal molecules that are small or hydrophobic can readily cross the plasma membrane use these receptors

15. Steroid hormone interacting with an intracellular receptor

16. Action of Steroid Hormones: • http://highered.mheducation.com/sites/0072995246/student_view0/chapter12/mechanism_of_steroid_hormone_action.html • http://highered.mheducation.com/sites/0072995246/student_view0/chapter12/how_intracellular_receptors_regulate_gene_transcription.html

17. Receptors in the Plasma Membrane There are three main types of membrane receptors: G-Protein-Linked:(epinephrine, neurotransmitters, pertussis, botulism, cholera) Tyrosine Kinases:(cell growth and reproduction) Ion Channels: (neurotransmitters, Na+, Ca++

18. The Structure of a G-Protein-Linked Receptor

19. The Functioning of a G-protein-Linked Receptor

20. Membrane-Bound Receptors That Activate G Proteins: http://novella.mhhe.com/sites/0070070017/student_view0/biology_1/chapter_11/membrane-bound_receptors_that_activate_g_proteins.html http://highered.mheducation.com/sites/9834092339/student_view0/chapter46/membrane-bound_receptors_that_activate_g_proteins.html

21. The Structure and Function of a Tyrosine-Kinase Receptor

22. A Ligand-Gated Ion-Channel Receptor

23. 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

24. Signal Transduction Pathways • At each step in a pathway the signal is transduced into a different form, commonly a conformational change in a protein

25. 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

26. A Phosphorylation Cascade

27. Small Molecules and Ions as Second Messengers • Second messengers are small, nonprotein, water-soluble molecules or ions • Cyclic AMP (cAMP) -made from ATP

28. cAMP as a Second Messenger

29. Secondary Messengers: cAMP • http://novella.mhhe.com/sites/0070070017/student_view0/biology_1/chapter_11/second_messenger__camp.html • G Proteins and Signal Amplification: http://novella.mhhe.com/sites/0070070017/student_view0/biology_1/chapter_45/signal_amplification.html

30. Calcium ions and Inositol Triphosphate (IP3) • Calcium, when released into the cytosol of a cell, acts as a second messenger in many different pathways

31. The maintenance of calcium ion concentrations in an animal cell

32. Other second messengers such as inositol triphosphate (IP3) and diacylglycerol (DAG) can trigger an increase in calcium in the cytosol

33. Calcium and Inositol Triphosphate in Signaling Pathways

34. Response: Cell signaling leads to regulation of cytoplasmic activities or transcription

35. Cytoplasmic response to a signal: the stimulation of glycogen breakdown by epinephrine

36. Nuclear response to a signal: the activation of a specific gene by a growth factor

37. Fine-Tuning of the Response • Signal pathways with multiple steps can amplify the signal and contribute to the specificity of the response

38. Signal Amplification • Each protein in a signaling pathway amplifies the signal by activating multiple copies of the next component in the pathway

39. Signal Amplification: • http://novella.mhhe.com/sites/0070070017/student_view0/biology_1/chapter_45/signal_amplification.html

40. 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

41. The Specificity of Cell Signaling

42. Scaffolding Proteins Increase Transduction Efficiency

43. Termination of the Signal • Signal response is terminated quickly by the reversal of ligand binding