1. Cell Communication Chapter 9

2. 2 Fig. 9.1

3. 3 Fig. 9.2

4. 4 Fig. 9.2.a

5. 5 Fig. 9.2.b

6. 6 Fig. 9.2.c

7. 7 Fig. 9.2.d

8. 8 Fig. 9.3

9. 9 Fig. 9.4.a

10. 10 Fig. 9.4.b

11. 11 Fig. 9.4.c

12. 12 Fig. 9.5

13. 13 Fig. 9.6

14. 14 Fig. 9.7

15. 15 Fig. 9.8

16. 16 Fig. 9.8.a

17. 17 Fig. 9.8.b

18. 18 Fig. 9.9

19. 19 Fig. 9.10

20. 20 Fig. 9.11

21. 21 Fig. 9.12

22. 22 Fig. 9.13

23. 23 Fig. 9.14

24. 24 Fig. 9.15

25. 25 Fig. 9.16

26. 26 Fig. 9.17

27. 27 Fig. 9.17.a(left)

28. 28 Fig. 9.17.a(right)

29. 29 Fig. 9.17.b(left)

30. 30 Fig. 9.17.b(right)

31. 31 Fig. 9.17.c(left)

32. 32 Fig. 9.17.c(right)

33. 33 Fig. 9.18

34. 34 Fig. 9.19

35. 35 Cell Communication Direct contact – molecules on the surface of one cell are recognized by receptors on the adjacent cell

36. 36 Cell Communication Paracrine signaling – signal released from a cell has an effect on neighboring cells

37. 37 Cell Communication Endocrine signaling – hormones released from a cell affect other cells throughout the body

38. 38 Cell Communication Synaptic signaling – nerve cells release the signal (neurotransmitter) which binds to receptors on nearby cells

39. 39 Cell Communication Communication between cells requires: ligand: the signaling molecule receptor protein: the molecule to which the receptor binds -may be on the plasma membrane or within the cell

40. 40 Cell Communication There are four basic mechanisms for cellular communication: 1. direct contact 2. paracrine signaling 3. endocrine signaling 4. synaptic signaling

41. 41 Cell Communication When a ligand binds to a receptor protein, the cell has a response. signal transduction: the events within the cell that occur in response to a signal Different cell types can respond differently to the same signal.

42. 42 Cell Communication A cell’s response to a signal often involves activating or inactivating proteins. Phosphorylation is a common way to change the activity of a protein. protein kinase – an enzyme that adds a phosphate to a protein phosphatase – an enzyme that removes a phosphate from a protein

43. 43 Receptor Types Receptors can be defined by their location. intracellular receptor – located within the cell cell surface receptor or membrane receptor – located on the plasma membrane to bind a ligand outside the cell

44. 44 Receptor Types There are 3 subclasses of membrane receptors: 1. channel linked receptors – ion channel that opens in response to a ligand 2. enzymatic receptors – receptor is an enzyme that is activated by the ligand 3. G protein-coupled receptor – a G- protein (bound to GTP) assists in transmitting the signal

45. 45 Intracellular Receptors steroid hormones -have a nonpolar, lipid-soluble structure -can cross the plasma membrane to a steroid receptor -usually affect regulation of gene expression An inhibitor blocks the receptor from binding to DNA until the hormone is present.

46. 46 Intracellular Receptors A steroid receptor has 3 functional domains: 1. hormone-binding domain 2. DNA binding domain 3. domain that interacts with coactivators to affect gene expression

47. 47 Receptor Kinases receptor tyrosine kinases -membrane receptor -when bound by a ligand, the receptor is activated by dimerization and autophosphorylation -activated receptor adds a phosphate to tyrosine on a response protein -an example is the insulin receptor

48. 48 Receptor Kinases kinase cascade – a series of protein kinases that phosphorylate each other in succession -amplifies the signal because a few signal molecules can elicit a large cell response mitogen-activated protein (MAP) kinases are activated by kinase cascades

49. 49 G-Protein Coupled Receptors G-protein – protein bound to GTP G-protein-coupled receptor (GPCRs) – receptors bound to G proteins -G-protein is a switch turned on by the receptor -G-protein then activates an effector protein (usually an enzyme)

50. 50 G-Protein Coupled Receptors Once activated, the effector protein produces a second messenger. -second messenger generates the cellular response to the original signal For example – one common effector protein is adenylyl cyclase which produces cAMP as a second messenger. Other second messengers: inositol phosphates, calcium ions (Ca 2+ )

51. 51 Cell-to-Cell Interactions Cells can identify each other by cell surface markers. -glycolipids are commonly used as tissue- specific markers -major histocompatibility complex (MHC) proteins are used by cells to distinguish “self” from “non-self”

52. 52 Cell-to-Cell Interactions Cells within a tissue are connected to each other by cell junctions 1. tight junctions – create sheets of cells 2. anchoring junctions – connect the cytoskeletons of adjacent cells 3. communicating junctions – permit small molecules to pass between cells a. gap junctions – in animal cells b. plasmodesmata – in plant cells