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In your notebook….

Explore the structure and function of the cell membrane, and compare it to a mosaic. Learn about the components, roles of membrane proteins, and how molecules cross the membrane. Discover the concepts of diffusion, osmosis, and tonicity.

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In your notebook….

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  1. In your notebook…. • Describe a mosaic, and then compare a cell membrane to it

  2. Two major components: • Phospholipids • Proteins

  3. Fluid Mosaic Model • http://www.susanahalpine.com/anim/Life/memb.htm • http://www.youtube.com/watch?v=ULR79TiUj80

  4. Roles of the membrane proteins • Move stuff across the membrane that can’t get across on its own • Recognition – like nametags • Receptors – trigger cellular responses • Enzymes

  5. It’s also called a lipid bi-layer

  6. HYDROPHILIC HYDROPHOBIC

  7. Back to your homework… • What kinds of molecules can cross the cell membrane, according to the diagram?

  8. Examples of small polar and nonpolar substances: • O2 • CO2 • H2O

  9. Homework diagram… • How do they cross? • In which direction do they cross?

  10. Make some predictions about your lab… • What do you think will happen to the mass of your cell? Why? • Which way do you think substances will move? Why?

  11. Compare your data with others. • You need to collect results from all three situations.

  12. Claim 1: Substances will diffuse across a permeable membrane. • Evidence: • Rationale/Reasoning:

  13. Claim 2: The cell membrane is selectively permeable. • Evidence: • Reasoning/Rationale:

  14. Role of the membrane? • Selective permeability

  15. Cell Membrane • Cell Membrane Animation • Made of phospholipids and proteins • Molecules move into and out of a cell through the cell membrane • The cell membrane is selectively permeable • How certain molecules move through the cell is called cell transport • Passive Transport • Active Transport

  16. Cell Transport

  17. Questions • What happens when you spray air freshener or perfume? • What happens when you put food coloring in water? • THIS IS DIFFUSION!!!! Diffusion is also one way things are transported across the cell membrane

  18. What is concentration? • Amount of solute in a certain amount of solvent…think about kool-aid… • Solvent – what does the dissolving (liquid) • Solute – what is dissolved in the solvent • Which is more concentrated?

  19. Diffusion Dynamic Equilibrium

  20. Make a hypothesis…. • Will the glucose move? Which way? Why or why not? • Will the iodine move? Which way? Why or why not? • Will the starch move? Which way? Why or why not?

  21. For lab… • To the tube, add: • Glucose solution • Starch • To the beaker, add: • Water • Iodine

  22. Flea Diffusion Analogy

  23. Flea Diffusion Analogy

  24. Dynamic Equilibrium

  25. Selectively permeable Definition Illustrate Selectively permeable What qualities might affect how easily a molecule can move through a membrane? Explain your illustration

  26. Sizes of Molecules… • Water (H2O) • Iodine (I2K) • Glucose (C6H12O6) • Food Coloring (~450 atoms) • Starch (~1000 atoms) So…how big are the pores of the membrane? Make an estimate

  27. How does the membrane regulate movement of molecules? • It’s structure dictates!!

  28. Two major components: • Phospholipids • Proteins

  29. HYDROPHILIC HYDROPHOBIC

  30. Examples of small polar and nonpolar substances: • O2 • CO2 • H2O

  31. Flea Diffusion Analogy

  32. Dynamic Equilibrium

  33. The fish can still move…so we call this DYNAMIC EQUILIBRIUM

  34. Lipid bi-layer • Fluid mosaic model • http://www.youtube.com/watch?v=Rl5EmUQdkuI • http://www.youtube.com/watch?v=GW0lqf4Fqpg

  35. Passive Transport • Particles move from high concentration to low concentration • Does NOT require extra cell energy • Includes simple diffusion, osmosis, facilitated diffusion

  36. SIMPLE DIFFUSION • Movement of molecules from areas of high concentration to areas of low concentration • Does not require energy (PASSIVE) • Because molecules are in constant, random, motion! • Will diffuse until reaches equilibrium (equal concentrations) • Dynamic equilibrium (still moving!)

  37. Simple Diffusion in Cells Diffusion Animation Diffusion Across a Membrane http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter38/diffusion_through_cell_membranes.html

  38. What kinds of things diffuse through the membrane? • SMALL AND UNCHARGED • Like carbon dioxide and oxygen.

  39. OSMOSIS • The diffusion of water across a membrane from an area of high concentration to low concentration • No energy required (PASSIVE TRANSPORT) • Occurs until reaches DYNAMIC EQUILIBRIUM • Equal concentrations on both sides of the membrane

  40. Tonicity of solutions • Used to compare the relative concentrations • Hypertonic • solution with a higher concentration of solute • So lower water concentration • Hypotonic • solution with a lower concentration of solute • So higher water concentration • Isotonic • solutions with equal concentrations of solute • Water diffuses from hypotonic solutions to hypertonic solutions!

  41. Cells in Hypertonic Solution HYPERTONIC • Water moves out of the cell • Cell shrivels Low Hi

  42. Hypotonic Solution • Water moves into the cell • Cell swells • Animal cell – can burst • Plant cell – builds up pressure on cell wall, but rigid cell wall keeps it from bursting HYPOTONIC Hi Lo

  43. Isotonic Solution • Water moves in and out of the cell • Cell stays the same size • Dynamic Equilibrium ISOTONIC

  44. Problem break

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