The Plasma Membrane -  Gateway to the Cell   1
Photograph of a Cell     Membrane                       2
Cell MembraneThe cell membrane is flexible and allows a unicellular organism to move                      3
Homeostasis• Balanced internal condition of  cells• Also called equilibrium• Maintained by plasma (or cell)  membrane cont...
Functions of Plasma           Membrane Protective fence Controls transport in & out of cell    (selectively permeable) ...
Functions of Plasma           Membrane Provide a tie on site for enzymes Place for cells to bind togetherContains the c...
Structure of the Cell Membrane                                 Peripheral                                 protein         ...
Phospholipids-3 modelsMake up the cell membraneContains 2 fattyacid chains thatare nonpolarHead is polar &contains a –PO4g...
FLUID MOSAIC MODEL           Fluid mosaic modelFLUID- because individual phospholipids and  proteins can move around freel...
• Mosaic           10
Cell MembranePolar heads are hydrophilic “water loving”Nonpolar tails are hydrophobic “water fearing”Makes membrane “Selec...
Cell MembraneThe cell membrane is madeof 2 layers of           Hydrophobic moleculesphospholipids called the pass easily; ...
Solubility• Materials that  are soluble in  lipids can pass  through the  cell membrane  easily                        13
Selectively Permeable          MembraneSmall molecules like water move acrosseasily, most larger molecules need help-and n...
IMPORTANT!Kinds of Transport    Across Cell    Membranes                     15
1. Passive TransportMovement of substances across the cell membrane without any input of   energy on the part of the cell....
2. Simple Diffusion• Requires NO  energy• Molecules move  from area of  HIGH to LOW  concentration or  down the  concentra...
Simple Diffusion continued• Concentration Gradient is the  difference ( change) in the  concentration of a substance from ...
DIFFUSIONDiffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINE...
Diffusion of Liquids                       20
Diffusion through a            Membrane                        Cell membraneSolute moves DOWN concentration gradient (HIGH...
Osmosis                       Diffusion across a membrane• Diffusion of water  across a  membrane• Moves from HIGH        ...
A Hypertonic solution has a higher concentration of dissolved particles than the cell.A Hypotonic solution has a lower con...
Diffusion of H2O Across A          MembraneHigh H2O potential         Low H2O potentialLow solute concentration   High sol...
Cell in Isotonic Solution   10% NaCL        ENVIRONMENT   90% H2O                CELL                                   NO...
Cell in Hypotonic Solution  10% NaCL  90% H2O               CELL              20% NaCL              80% H2OWhat is the dir...
Cell in Hypertonic Solution   15% NaCL      ENVIRONMENT   85% H2O                CELL               5% NaCL               ...
Cells in Solutions                     28
Isotonic Solution     Hypotonic         Hypertonic                       Solution          Solution     NO NET MOVEMENT OF...
Osmosis in Red Blood CellsIsotonic   Hypotonic   Hypertonic                              30
Osmosis in plant cellsIn plant cells, plasmolysis results in wilting and osmotic pressure results in turgor pressure.     ...
hypotonic     hypertonic   isotonic hypertonic   isotonic      hypotonic                                        32
Three Forms of Transport Across the Membrane                                        33
Passive Transport    Simple Diffusion Doesn’t require energy Moves high to lowconcentration Example: Oxygen orwater dif...
Facilitated diffusionDoesn’t require energyUses transportproteins to move high tolow concentrationExamples: Glucose oram...
Proteins Are Critical to  Membrane Function                           36
Types of Transport Proteins• Channel proteins are embedded  in the cell membrane & have a  pore for materials to cross• Ca...
Facilitated DiffusionMolecules will randomly move throughthe pores in Channel Proteins.                                   38
Facilitated Diffusion• Some Carrier  proteins do not  extend through  the membrane.• They bond and  drag molecules  throug...
Carrier Proteins• Other carrier  proteins  change shape  to move  materials  across the cell  membrane                    ...
Remember this? It’s Facilitated Passive     Transport.                       41
Passive Transport ReviewMovement of particles across the cell membrane without energy input on the part of the cell.      ...
Passive Transport ReviewThree major types:1) Diffusion2) Osmosis3) Facilitated Diffusion                           43
Active Transport                   44
Active TransportRequires energy orATPMoves materials fromLOW to HIGHconcentrationAGAINSTconcentration gradient         ...
Major Types• Endocytosis (including pinocytosis and phagocytosis)• Exocytosis• Pumps (including proton pump and sodium-pot...
Endocytosis              47
Endocytosis• Endocytosis is the process of taking  liquids or larger molecules into a cell  by engulfing them in a membran...
Moving the “Big Stuff”Large molecules move materials into the cell by      one of three forms of endocytosis.             ...
Pinocytosis• Endocytosis  that involves  movement of  liquids.• Called “Cell  Drinking”                          50
PinocytosisMost common form of endocytosis.Takes in dissolved molecules as a vesicle.                                     ...
Example of Pinocytosispinocytic vesicles forming               mature transport vesicle                                   ...
Endocytosis – Phagocytosis  •Endocytosis that involves taking  in        large particles such as food, bacteria, etc. into...
Phagocytosis About to Occur                          54
Phagocytosis- Captureof a YeastCell (yellow)byMembraneExtensionsof anImmuneSystem Cell(blue)                55
Exocytosis• moving things out• essentially the opposite of endocytosis• Molecules are moved out of the cell by  vesicles t...
Exocytosis             57
Exocytosis       Exocytic       vesicle       immediately       after fusion       with plasma       membrane.            ...
ExocytosisThe opposite of endocytosis is exocytosis. Largemolecules that are manufactured in the cell are     released thr...
Pumps• Pumps are similar to  facilitated diffusion in  that they use transport  proteins.• Pumps use proteins to  move mat...
Three Types of Pumps• Sodium-Potassium Pump (3 Na out,  2 K in)• Proton Pump• Contractile Vacuole (pumps excess  water out...
Sodium-Potassium Pump   3 Na+ pumped out for every 2 K+pumped in; creates a membrane potential                            ...
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Cell membranes and transport

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Cell membranes and transport

  1. 1. The Plasma Membrane - Gateway to the Cell 1
  2. 2. Photograph of a Cell Membrane 2
  3. 3. Cell MembraneThe cell membrane is flexible and allows a unicellular organism to move 3
  4. 4. Homeostasis• Balanced internal condition of cells• Also called equilibrium• Maintained by plasma (or cell) membrane controlling what enters & leaves the cell 4
  5. 5. Functions of Plasma Membrane Protective fence Controls transport in & out of cell (selectively permeable) Allow cells recognize “friend or Foe” Provide anchoring sites thecytoskeleton support framework 5
  6. 6. Functions of Plasma Membrane Provide a tie on site for enzymes Place for cells to bind togetherContains the cytoplasm (fluid in cell) 6
  7. 7. Structure of the Cell Membrane Peripheral protein Lipid Bilayer Integral Protein 7
  8. 8. Phospholipids-3 modelsMake up the cell membraneContains 2 fattyacid chains thatare nonpolarHead is polar &contains a –PO4group 8
  9. 9. FLUID MOSAIC MODEL Fluid mosaic modelFLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid.MOSAIC-little pieces put together in a pattern 9
  10. 10. • Mosaic 10
  11. 11. Cell MembranePolar heads are hydrophilic “water loving”Nonpolar tails are hydrophobic “water fearing”Makes membrane “Selective” in what crosses11
  12. 12. Cell MembraneThe cell membrane is madeof 2 layers of Hydrophobic moleculesphospholipids called the pass easily; hydrophilliclipid bilayer DO NOT 12
  13. 13. Solubility• Materials that are soluble in lipids can pass through the cell membrane easily 13
  14. 14. Selectively Permeable MembraneSmall molecules like water move acrosseasily, most larger molecules need help-and need energy to be added so they cancross. 14
  15. 15. IMPORTANT!Kinds of Transport Across Cell Membranes 15
  16. 16. 1. Passive TransportMovement of substances across the cell membrane without any input of energy on the part of the cell. 16
  17. 17. 2. Simple Diffusion• Requires NO energy• Molecules move from area of HIGH to LOW concentration or down the concentration gradient. 17
  18. 18. Simple Diffusion continued• Concentration Gradient is the difference ( change) in the concentration of a substance from one location to another. 18
  19. 19. DIFFUSIONDiffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY 19
  20. 20. Diffusion of Liquids 20
  21. 21. Diffusion through a Membrane Cell membraneSolute moves DOWN concentration gradient (HIGH to LOW) until equilibrium is reached 21
  22. 22. Osmosis Diffusion across a membrane• Diffusion of water across a membrane• Moves from HIGH Semipermeable water potential membrane (low solute) to LOW water potential (high solute) 22
  23. 23. A Hypertonic solution has a higher concentration of dissolved particles than the cell.A Hypotonic solution has a lower concentration of dissolved particles than the cell.An Isotonic solution has the same concentration of dissolved particles as the cell. 23
  24. 24. Diffusion of H2O Across A MembraneHigh H2O potential Low H2O potentialLow solute concentration High solute concentration 24
  25. 25. Cell in Isotonic Solution 10% NaCL ENVIRONMENT 90% H2O CELL NO NET 10% NaCL MOVEMENT 90% H2OWhat is the direction of water movement? equilibrium The cell is at _______________. 25
  26. 26. Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2OWhat is the direction of water movement? 26
  27. 27. Cell in Hypertonic Solution 15% NaCL ENVIRONMENT 85% H2O CELL 5% NaCL 95% H2OWhat is the direction of water movement? 27
  28. 28. Cells in Solutions 28
  29. 29. Isotonic Solution Hypotonic Hypertonic Solution Solution NO NET MOVEMENT OFH2O (equal amounts CYTOLYSIS PLASMOLYSISentering & leaving) (cell rupture) (cell shrinkage) 29
  30. 30. Osmosis in Red Blood CellsIsotonic Hypotonic Hypertonic 30
  31. 31. Osmosis in plant cellsIn plant cells, plasmolysis results in wilting and osmotic pressure results in turgor pressure. 31
  32. 32. hypotonic hypertonic isotonic hypertonic isotonic hypotonic 32
  33. 33. Three Forms of Transport Across the Membrane 33
  34. 34. Passive Transport Simple Diffusion Doesn’t require energy Moves high to lowconcentration Example: Oxygen orwater diffusing into acell and carbon dioxidediffusing out. 34
  35. 35. Facilitated diffusionDoesn’t require energyUses transportproteins to move high tolow concentrationExamples: Glucose oramino acids moving fromblood into a cell. 35
  36. 36. Proteins Are Critical to Membrane Function 36
  37. 37. 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 37
  38. 38. Facilitated DiffusionMolecules will randomly move throughthe pores in Channel Proteins. 38
  39. 39. Facilitated Diffusion• 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. 39
  40. 40. Carrier Proteins• Other carrier proteins change shape to move materials across the cell membrane 40
  41. 41. Remember this? It’s Facilitated Passive Transport. 41
  42. 42. Passive Transport ReviewMovement of particles across the cell membrane without energy input on the part of the cell. 42
  43. 43. Passive Transport ReviewThree major types:1) Diffusion2) Osmosis3) Facilitated Diffusion 43
  44. 44. Active Transport 44
  45. 45. Active TransportRequires energy orATPMoves materials fromLOW to HIGHconcentrationAGAINSTconcentration gradient 45
  46. 46. Major Types• Endocytosis (including pinocytosis and phagocytosis)• Exocytosis• Pumps (including proton pump and sodium-potassium pump) 46
  47. 47. Endocytosis 47
  48. 48. Endocytosis• Endocytosis is the process of taking liquids or larger molecules into a cell by engulfing them in a membrane.• This is done when the cell membrane makes a pocket around the substance that breaks off inside the cell.• This pocket is called a vesicle. 48
  49. 49. Moving the “Big Stuff”Large molecules move materials into the cell by one of three forms of endocytosis. 49
  50. 50. Pinocytosis• Endocytosis that involves movement of liquids.• Called “Cell Drinking” 50
  51. 51. PinocytosisMost common form of endocytosis.Takes in dissolved molecules as a vesicle. 51
  52. 52. Example of Pinocytosispinocytic vesicles forming mature transport vesicle 52 Transport across a capillary cell (blue).
  53. 53. Endocytosis – Phagocytosis •Endocytosis that involves taking in large particles such as food, bacteria, etc. into vesicles •Called “Cell Eating” 53
  54. 54. Phagocytosis About to Occur 54
  55. 55. Phagocytosis- Captureof a YeastCell (yellow)byMembraneExtensionsof anImmuneSystem Cell(blue) 55
  56. 56. Exocytosis• moving things out• essentially the opposite of endocytosis• Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.• This is how many hormones are secreted and how nerve cells communicate with one another 56
  57. 57. Exocytosis 57
  58. 58. Exocytosis Exocytic vesicle immediately after fusion with plasma membrane. 58
  59. 59. ExocytosisThe opposite of endocytosis is exocytosis. Largemolecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment 59
  60. 60. Pumps• Pumps are similar to facilitated diffusion in that they use transport proteins.• Pumps use proteins to move materials against the concentration gradient. 60
  61. 61. Three Types of Pumps• Sodium-Potassium Pump (3 Na out, 2 K in)• Proton Pump• Contractile Vacuole (pumps excess water out of single-cell organisms) 61
  62. 62. Sodium-Potassium Pump 3 Na+ pumped out for every 2 K+pumped in; creates a membrane potential 62

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