1. 1 The Plasma Membrane The Plasma Membrane - Gateway to the Cell copyright cmassengale

2. 2 Photograph of a Cell Membrane copyright cmassengale

3. 3 Cell Membrane flexible The cell membrane is flexible and allows a unicellular organism to move copyright cmassengale

4. 4 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma membrane controlling what enters & leaves the cell copyright cmassengale

5. 5 Structure of the Cell Membrane copyright cmassengale

6. 6 FLUID- because individual phospholipids and proteins can move side-to-side within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. FLUID MOSAIC MODEL copyright cmassengale

7. 7 hydrophilic Polar heads are hydrophilic “water loving ” hydrophobic Nonpolar tails are hydrophobic “water fearing” Cell Membrane Makes membrane “Selective” in what crosses copyright cmassengale

8. 8 Solubility Materials that are soluble in lipids can pass through the cell membrane easily copyright cmassengale

9. 9 Small molecules and larger hydrophobic molecules move through easily. e.g. O 2, CO 2, H 2 O Semipermeable Membrane copyright cmassengale

10. 10 Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. Semipermeable Membrane copyright cmassengale

11. 11 Types of Transport Across Cell Membranes copyright cmassengale

12. Concentration – the amount of a substance dissolved in a unit of another substance Passive Transport

13. Concentration gradient – difference in concentration of a particular molecule between two regions Net movement of molecules tends to be down a concentration gradient Passive Transport

14. Passive transport –process of molecular movement which does not require energy Three types: –Diffusion –Facilitated diffusion –Osmosis Passive Transport

15. 15 Simple Diffusion NORequires NO energy HIGH to LOWMolecules move from area of HIGH to LOW concentration copyright cmassengale

16. 16 DIFFUSION PASSIVE Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY copyright cmassengale

17. 17 Diffusion of Liquids copyright cmassengale

18. 18 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) copyright cmassengale

19. 19 Osmosis Diffusion of water across a membraneDiffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute)Moves from HIGH water potential (low solute) to LOW water potential (high solute) Diffusion across a membrane Semipermeable membrane copyright cmassengale

20. Concentrations of solutions –Isotonic – concentrations of both solutions are equal –Hypertonic – more concentrated solution –Hypotonic – less concentrated solution Osmosis – diffusion of water molecules from an area of higher concentration to an area of lower concentration Osmosis

21. Net movement of water molecules is toward hypertonic side of membrane Osmosis Across a Membrane

22. 22 Diffusion of H 2 O Across A Membrane High H 2 O potential Low solute concentration Low H 2 O potential High solute concentration copyright cmassengale

23. 23 Cell in Isotonic Solution CELL 10% NaCL 90% H 2 O 10% NaCL 90% H 2 O What is the direction of water movement? The cell is at _______________. equilibrium ENVIRONMENT NO NET MOVEMENT copyright cmassengale

24. 24 Cell in Hypotonic Solution CELL 10% NaCL 90% H 2 O 20% NaCL 80% H 2 O What is the direction of water movement? copyright cmassengale

25. 25 Cell in Hypertonic Solution CELL 15% NaCL 85% H 2 O 5% NaCL 95% H 2 O What is the direction of water movement? ENVIRONMENT copyright cmassengale

26. 26 Cells in Solutions copyright cmassengale

27. 27 Isotonic Solution NO NET MOVEMENT OF H 2 O (equal amounts entering & leaving) Hypotonic Solution CYTOLYSIS Hypertonic Solution PLASMOLYSIS copyright cmassengale

28. Animal cells function best in isotonic environment Plant cells function best in hypotonic environment –Turgor – cells become rigid due to osmotic pressure Osmosis

29. What Happens to Blood Cells? copyright cmassengale29

30. 30 hypotonichypertonic isotonic hypertonicisotonic hypotonic copyright cmassengale

31. 31 Three Forms of Transport Across the Membrane copyright cmassengale

32. 32 Passive Transport Simple Diffusion  Doesn’t require energy  Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out  Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out. copyright cmassengale

33. 33 Passive Transport Facilitated diffusion  Doesn’t require energy  Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. copyright cmassengale

34. 34 Proteins Are Critical to Membrane Function copyright cmassengale

35. 35 Types of Transport Proteins Channel proteins are embedded in the cell membrane & have a pore for materials to cross Carrier proteins can change shape to move material from one side of the membrane to the other copyright cmassengale

36. 36 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. copyright cmassengale

37. 37 Facilitated Diffusion Some Carrier proteins do not extend through the membrane.Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side.They bond and drag molecules through the lipid bilayer and release them on the opposite side. copyright cmassengale

38. 38 Carrier Proteins Other carrier proteins change shape to move materials across the cell membraneOther carrier proteins change shape to move materials across the cell membrane copyright cmassengale

39. 39 Active Transport  Requires energy or ATP  Moves materials from LOW to HIGH concentration  AGAINST concentration gradient copyright cmassengale

40. Active transport – process of molecular movement which requires energy Moves molecules against concentration gradients using ion pumps and cotransport Ion pump – membrane protein that pumps ions one-way against the ion’s concentration gradient Active Transport

41. 41 Active transport  Examples: Pumping Na + (sodium ions) out and K + (potassium ions) in against strong concentration gradients.  Called Na+-K+ Pump copyright cmassengale

42. 42 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential copyright cmassengale

43. 43 Moving the “Big Stuff” Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. Exocytosis Exocytosis - moving things out. This is how many hormones are secreted and how nerve cells communicate with one another This is how many hormones are secreted and how nerve cells communicate with one another. copyright cmassengale

44. 44 Exocytosis Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment copyright cmassengale

45. 45 Exocytosis Exocytic vesicle immediately after fusion with plasma membrane. copyright cmassengale

46. 46 Moving the “Big Stuff” Large molecules move materials into the cell by endocytosis Large molecules move materials into the cell by endocytosis. copyright cmassengale

47. 47 Example of Endocytosis endocytic vesicles forming mature transport vesicle Transport across a capillary cell (blue). copyright cmassengale

48. 48

49. 49 Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating” copyright cmassengale

50. 50

51. 51 Phagocytosis About to Occur copyright cmassengale

52. 52 Phagocytosis Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) copyright cmassengale