1. CELL STRUCTURE & FUNCTION Dr. Michael C. Potter Paul VI Catholic High School 2006

2. CELL STRUCTURE & FUNCTION CELL MEMBRANES The cell membrane is the interface between the internal and the external environment of the cell. Cell membranes encase ALL living cells Cell membranes are two molecules thick (10 nm)

3. CELL STRUCTURE & FUNCTION

5. I.Structure of Cell Membrane: A. Bilayer Lipid Membrane 1. Amphipathic (Polar) a. hydrophilic head (outside) b. hydrophobic head (inside)

6. CELL STRUCTURE & FUNCTION

7. 2. Type of Phospholipid determine permeability a. Double bond vs. Single bond b. Long tail vs. Short tail B. Proteins: Multiple Function/Structure

8. CELL STRUCTURE & FUNCTION

9. C. Cholesterol 1. Fluidity Buffer: a. Increase viscosity at high temp b. Decrease viscosity at low temp 2. Strengthens Membrane a. Fills gaps between tails of lipids with double bonds

10. CELL STRUCTURE & FUNCTION D. Temperature Effect: 1. High Temp-low viscosity high permeability 2. Low Temp-high viscosity low permeability E. Models of Membranes 1. Davson-Danielli Model (1935) 2. Fluid Mosaic Model (1972)

11. CELL STRUCTURE & FUNCTION

14. II. Components of Cell Membranes: A. Lipid Bilayer B. Membrane Proteins: 1. Integral Membrane Proteins a. Three Domains: Cytosolic Face Exoplasmic Face Membrane Spanning Domain

15. CELL STRUCTURE & FUNCTION

17. B. Membrane Proteins: 1. Integral Membrane Proteins: b. Allow Movement Thru Membrane c. Anchor Membranes d. Act as Receptors e. Function as Enzymes f. Signal Transduction g. Cell-Cell Recognition

18. CELL STRUCTURE & FUNCTION B. Membrane Proteins: 1. Integral Membrane Proteins: h. Types: 1. Transmembrane Proteins 2. Membrane Associated Proteins 3. Lipid-Linked Proteins 4. Protein Attached

19. CELL STRUCTURE & FUNCTION

20. Ex. Of “Glycocalyx”

21. CELL STRUCTURE & FUNCTION B. MEMBRANE PROTEINS: Transmembrane Proteins: a. Single Pass: (Glycophorin in RBC) b. Multipass: Channels, Pores, Gates β- Barrel Porin Proteins

22. CELL STRUCTURE & FUNCTION

24. MEMBRANE PORE PROTEIN

25. CELL STRUCTURE & FUNCTION

26. B. MEMBRANE PROTEINS: Membrane Associated Proteins: Exoplasmic Face: Anchors Receptors Signaling Proteins Attachment Proteins Recognition Proteins

27. CELL STRUCTURE & FUNCTION CELL RECOGNITION (IDENT.) PROTEIN

28. CELL STRUCTURE & FUNCTION

29. B. MEMBRANE PROTEINS: Membrane Associated Proteins: Cytosolic Face: Attachment Proteins (Spectrin-RBC’s) Anchors Structural Proteins Signaling Proteins

30. CELL STRUCTURE & FUNCTION III. CELL JUNCTIONS: A. OCCLUDING JUNCTIONS: Seal cells so tightly together to prevent even a small molecule from leaking across Seen in vertebrates Also called “Tight Junctions” Example: occludin, claudins

31. CELL STRUCTURE & FUNCTION Occluding junction (Tight Junction)

32. CELL STRUCTURE & FUNCTION III. CELL JUNCTIONS: B. ANCHORING JUNCTIONS: Mechanically attaches cell to its neighbors ….e.g. Desmosomes: “cell rivets” attach to intermediate filament Adherens: Attach to actin fibers Cadherins

33. CELL STRUCTURE & FUNCTION ANCHORING JUNCTION

34. CELL STRUCTURE & FUNCTION III. CELL JUNCTIONS: B. ANCHORING JUNCTIONS: Focal Adhesions Hemidesmosomes Bind cells to extracellular matrix (integrin proteins)

35. CELL STRUCTURE & FUNCTION ANCHORING JUNCTION

36. CELL STRUCTURE & FUNCTION III. CELL JUNCTIONS: C. COMMUNICATING JUNCTIONS: Mediate the passage of chemical or electrical signals from cell-cell; a direct cytoplasmic link. 1. Gap Junctions (animals) 2. Plasmodesmata (plants) 3. Synapses (nerve cells)

37. CELL STRUCTURE & FUNCTION Communicating Junction

38. CELL STRUCTURE & FUNCTION Communicating Junction

39. CELL STRUCTURE & FUNCTION PLASMODESMATA

40. CELL STRUCTURE & FUNCTION PLASMODESMATA

41. CELL STRUCTURE & FUNCTION

44. SYMPORTER

45. CELL STRUCTURE & FUNCTION 1. Integral Membrane Proteins (cont’d) b. Movement through Membranes - Active Transport REQUIRES ENERGY Moves against a gradient Na-K Pump Maintains Osmotic balance Maintains transmembrane electrical potential

46. CELL STRUCTURE & FUNCTION ACTIVE TRANSPORT

47. CELL STRUCTURE & FUNCTION 2. Lipid-Anchored Membrane Protein: Extend partially thru membrane Bound to one or more lipids 3. Peripheral (exterior) Proteins: Do not interact with hydrophobic core Localized to cytosolic or exoplasmic face

48. CELL STRUCTURE & FUNCTION C. Network of Support Fibers 1. Often Intermediate Filaments a. Vimentins b. Desmins c. Spectrin: determines shape of cell, whereas… d. Clathrins: anchor proteins to certain sites.

49. CELL STRUCTURE & FUNCTION D. Exterior Protein & Glycoprotein 1. Glycocalyx 2. Cell identity markers

50. CELL STRUCTURE & FUNCTION Kinds of Membrane Proteins 1. Transport Channels: a. Single Pass b. Multipass 2. Enzymes a. Attached to membrane b. Function on interior of membrane 3. Cell Surface Receptor a. Act as “antennae”

51. CELL STRUCTURE & FUNCTION Kinds of Membrane Proteins 4. Cell Surface Identity Markers 5. Cell Adhesion Proteins 6. Attachments to Cytoskeleton Linking proteins

52. CELL STRUCTURE & FUNCTION Movement Through Membranes 1. DIFFUSION: a. Moves with gradient b. Dependent on selective permeability c. May utilize channels or pores e.g. movement of ions d. “Passive” process

53. CELL STRUCTURE & FUNCTION 2. FACILITATED DIFFUSION a.

54. CELL STRUCTURE & FUNCTION

57. 1.Integral Membrane Proteins (cont’d) b. Movement through Membranes - Cotransport: Requires transmembrane protein or “carrier” protein Uniporter Symporter Antiporter Secondary “Active Transport”

58. CELL STRUCTURE & FUNCTION

61. COTRANSPORT

62. CELL STRUCTURE & FUNCTION