1. Chapter 11 Communication

2. Cell communication

3. Traditional Ethiopian coffee ceremony

4. Caffeine Sends signals to Blood vessels Brain Liver Heart

5. Yeast cells

6. Bacteria

7. NO

8. Cell communication Coordinates cell behavior Body functions as a whole. Hallmark of multicellular organisms. Evolution Single cell organisms communicate.

9. Cell communication Cells are exposed to a continuous stream of signals. Signals come from the environment surrounding the cell. Signals can be from another cell. Chemical signals

10. Peptides Proteins Amino acid Nucleotides Steroids or other lipids NO or Nitric oxide

11. Types of cell signaling Depend on location of cells 1. Direct contact 2. Local signaling A. Paracrine signaling B.Synaptic signaling 3. Long-distance signaling Endocrine Nerve electrical impulse

12. 1. Direct contact Gap junction: Animal cells Plasmodesmata: Plant cells Chemical or electrical impulse

13. 1. Direct contact When cells are close Molecules on one cell are recognized by the plasma membrane of another cell. Many interactions between cells in early development occur this way.

14. 2. Local signaling A. Paracrine signaling Short-lived signals with local effects. Growth factors Play an important role in early development

15. Local signaling B. Synaptic signaling Involves the nervous system Neurotransmitters: Signal molecules Chemical synapse: Communication be neuron & the target cell

16. Long distance Signaling Endocrine signaling Molecules that remain in the extracellular fluid Enter the bloodstream Affect cells very far from where released Hormones: longer-lived signal molecules

17. Long distance signaling Nerve cell Electrical impulse along the neuron

18. Signal transduction pathway The signal causes a response in the cell

19. Fig. 11-14 Growth factor Receptor Phosphorylation cascade Reception Transduction Active transcription factor Response P Inactive transcription factor CYTOPLASM DNA NUCLEUS mRNA Gene

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21. Signal transduction pathway Reception: Signal is detected Molecule binds a receptor protein Located on surface or inside

22. Signal transduction pathway Transduction: Signaling molecule changes receptor Changes signal so it can cause a response Single step Multiple steps

23. Signal transduction pathway Response: Stimulates a specific cellular response Correct cell Correct response

24. Reception Ligand: Molecule that binds specifically to another molecule Activates the receptor protein Receptor protein undergoes change in shape

25. Reception Most receptors are plasma membrane proteins Signal (ligand) large, water soluble

26. Receptors A. Intracellular receptors. B. Cell surface receptors. 1. Ion-channel receptors 2. Tyrosine kinases 3. G-protein-coupled receptors

27. A. Intracellular receptors Lipid-soluble signaling molecule Small molecule Able to cross the membrane Interacts with a receptor inside. Bind protein receptors in the cytoplasm Bind protein receptors in the nucleus

28. A. Intracellular receptors 1. Act as regulators of gene expression Activate or suppress expression of certain genes Cortisol, testosterone, estrogen & progesterone are signal molecules.

29. Fig. 11-8-5 Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein Plasma membrane Hormone- receptor complex DNA mRNA NUCLEUS New protein CYTOPLASM

30. A. Intracellular receptors 2. Receptors act as enzymes Example: NO Binds a receptor. Activates the enzyme to catalyze the synthesis of GMP Relax smooth muscle Causing blood vessels to relax Causes an increased blood flow

31. B. Cell surface receptors Many signal molecules are water soluble Unable to pass through membrane Bind a receptor on the surface Causes a change inside cell.

32. B. Cell surface receptors 1. Ion channels (Chemically gated) Receptor proteins that allow ions to pass through Opens only when a signal molecule (ligand) binds to receptor. Ions are sodium, potassium, calcium or chlorine. Gate closes when ligand is released Example of signal molecule-neurotransmitter

34. 2. Tyrosine Kinases Single molecules bind receptor outside the cell Stimulates receptor to activate the enzyme in the cytoplasm These enzymes catalyze the transfer of phosphate groups

35. 2. Tyrosine Kinases Phosphorolated receptor Addition of phosphates to receptor Triggers a cell response Can trigger more than one response

36. Fig. 11-7c Signaling molecule (ligand) Ligand-binding site  Helix Tyrosines Tyr Receptor tyrosine kinase proteins CYTOPLASM Signaling molecule Tyr Dimer Activated relay proteins Tyr P P P P P P Cellular response 1 Cellular response 2 Inactive relay proteins Activated tyrosine kinase regions Fully activated receptor tyrosine kinase 6 6 ADP ATP Tyr P P P P P P 1 2 3 4

37. G-protein coupled receptor

39. G-protein

40. GDP vs GTP

41. 3. G-protein-linked receptors G-protein Inactive: GDP (guanosine diphosphate) Active: GTP (guanosine triphosphate) Signal molecule binds the receptor Activates the receptor Activates the G-protein G-protein then initiates a series of events It can open an ion channel or stimulate an enzyme

42. G-protein It is a short lived response Dependent on continued extracellular stimulation

43. Fig. 11-7b G protein-coupled receptor Plasma membrane Enzyme G protein (inactive) GDP CYTOPLASM Activated enzyme GTP Cellular response GDP P i Activated receptor GDP GTP Signaling molecule Inactive enzyme 1 2 3 4

45. Transduction Relay of signals from receptors to target cell Multiple steps Amplify the signal Coordination of simple processes

46. Transduction Proteins (signal molecule) Phosphorylation cascade Transfer a phosphate from an ATP to a protein Enzyme: protein kinase Protein causes cellular response Abnormal kinase activity can result in abnormal cell growth or cancer

47. Phosphorylation cascade

48. Inactivation Protein phosphatases Enzymes that remove phosphates Turns off mechanism Balance of the phosphorylation/dephosphorylation regulate activities of the cell

49. Second messengers Non-protein, small, water-soluble molecules or ions Diffuse quickly in the cytoplasm Relay messages from the receptor to the target cells G protein-coupled & tyrosine kinase pathways

50. Second messengers Cyclic AMP (cAMP) Cyclic adenosine monophophate Calcium ions

51. cAMP pathway Signal molecule attaches to the surface receptor. Activates the G receptor Activates the enzyme adenylyl cyclase to make cAMP. cAMP then activates the target protein

52. cAMP pathway Amplifies signal Short-lived Phosphodiesterases (enzyme) Converts cAMP to AMP

53. cAMP pathway

57. Cholera Bacteria Causes diarrhea Toxin Blocks the inhibitory enzyme G-protein remains active- Stimulates adenylyl cyclase Makes excessive amounts of cAMP Causes intestines to secrete ions (salts)

58. Nitrates Smooth muscle relaxation Dilation of blood vessels Block the inhibitory enzyme Prolongs cGMP Continues affect

59. Calcium ions Ca ion cytoplasmic levels usually low Increased Ca levels can cause Muscle contraction Cell division Hormone release

60. Calcium ions Signal molecule attaches to the surface receptor Activates the G receptor Which activates the enzyme phospholipase C. Which activates IP 3 Which causes the ER to release Ca ions Ca ions cause affect

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63. Response Regulation of a cellular activity Nucleus or cytoplasm Protein synthesis Activity of a protein

65. Response Fine-tuning Amplification Specificity Scaffolding protein Helps enhance response

68. Apoptosis Programmed cell death Chop cells that are damaged Protects surrounding cells Embryonic cell growth

69. Fig. 11-19 2 µm

70. Apoptosis Caspase Enzymes that regulate cell death Signal outside of cell Nucleus can signal (DNA gone bad) ER (Protein misfolding)

71. Apoptosis Webbed feet or hands Parkinson’s or Alzheimer’s Cancer (melanoma)

72. Fig. 11-21 Interdigital tissue 1 mm