(B) Diffusion And Osmosis


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(B) Diffusion And Osmosis

  1. 1. Cells and Diffusion <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Name the method by which substances move in </li></ul><ul><li>and out of cells </li></ul><ul><li>Define diffusion </li></ul><ul><li>State when diffusion will stop </li></ul><ul><li>From diagrams, predict the direction of </li></ul><ul><li>movement of substances by diffusion </li></ul><ul><li>State which substances enter and leave living </li></ul><ul><li>cells by diffusion </li></ul><ul><li>Give one reason why diffusion is important to </li></ul><ul><li>whole organisms </li></ul>
  2. 2. <ul><li>Substances have to pass into and out of cells </li></ul><ul><li>These movements most commonly occur by diffusion </li></ul>Diffusion is the movement of molecules from an area of HIGH concentration to an area of LOW concentration until they are EVENLY spread
  3. 3. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html Animation of diffusion Click on address to view
  4. 4. Food molecules Oxygen molecules Carbon dioxide molecules Diffusion in or out of a living cell
  5. 5. Cells and Osmosis <ul><li>Today’s Learning Objectives: </li></ul><ul><li>Name the method by which water passes in </li></ul><ul><li>and out of cells </li></ul><ul><li>Explain what a selectively permeable membrane is </li></ul><ul><li>State what osmosis is using the terms </li></ul><ul><li>selectively permeable membrane and concentration </li></ul><ul><li>gradient </li></ul><ul><li>Identify water concentration gradients when </li></ul><ul><li>given solute concentrations </li></ul><ul><li>Predict the direction of water movement between </li></ul><ul><li>two solutions of know concentration </li></ul><ul><li>Describe and predict a visking tubing experiment </li></ul>
  6. 6. OSMOSIS is the special diffusion of WATER from a HIGH WATER concentration to a LOW WATER concentration through a SELECTIVELY PERMEABLE MEMBRANE A membrane which is selectively permeable allows certain molecules to pass through but not others.
  7. 7. Membrane fully permeable to small molecules e.g. water Membrane slowly permeable to larger molecules e.g. sugar Membrane is not permeable to huge molecules e.g. starch Selectively permeable membrane Nucleus Cytoplasm
  8. 8. Concentration Gradient 99% water 1% sugar 95% water 5% sugar Higher concentration of water Lower concentration of water
  9. 9. Lower concentration of water Higher concentration of water Water moves down a concentration gradient by OSMOSIS from high to low concentration Water molecule Sugar molecule Selectively permeable membrane
  10. 10. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html Osmosis Animation Click on address to view
  11. 11. Water Concentrations A dilute sugar solution has a high water concentration A concentrated solutions has a low water concentration Water moves in or out of a cell depending on whether the water concentration outside the cell is higher or lower than the water concentration inside the cell
  12. 12. Water will move into the cell Water will move out of the cell Water concentration is equal inside and outside the cell. Solution outside is hypotonic Solution outside is Hypertonic Solution outside is isotonic
  13. 13. Hypotonic, Hypertonic, Isotonic <ul><li>Hypotonic . Has a higher water concentration and a low solute concentration….. </li></ul><ul><li>Hypertonic Has a lower water concentration and a high solute concentration….. </li></ul><ul><li>Isotonic Has a water concentration and solute concentration the same…… </li></ul><ul><li>as the solution in contact </li></ul>