Diffusion and osmosis homework powerpoint


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  • SQA LO: Hypertonic, isotonic, hypotonic
  • Diffusion and osmosis homework powerpoint

    1. 1. Diffusion
    2. 2. Fill in the blanks on your sheet as we go through the ppt Diffusion Diffusion is the movement of molecules from an area of high concentration to an area of low concentration, until evenly spread out.
    3. 3. Why is diffusion important? All living cells rely on diffusion to live. They use it for: <ul><li>getting raw materials for respiration (dissolved substances and gases) </li></ul><ul><li>removing waste products (eg. from respiration) </li></ul><ul><li>photosynthesis in plants (raw materials in, waste products out) </li></ul>Examples…
    4. 4. Respiration- gas exchange In breathing you exchange carbon dioxide (CO 2 ) and oxygen (O 2 ) between alveoli in the lungs and the blood. This is an example of diffusion . SEM photos of lung alveoli
    5. 5. Respiration- in cells food + oxygen  carbon dioxide + water + energy
    6. 6. Respiration & diffusion
    7. 7. Photosynthesis & Diffusion <ul><li>Carbon dioxide diffuses in through the stomata </li></ul><ul><li>Oxygen and water diffuse out of the stomata </li></ul>carbon dioxide + water  oxygen + glucose
    8. 8. Osmosis Osmosis is a special case of diffusion. It is the net movement of water across a selectively permeable membrane from a high concentration to a low concentration . The cell membrane has very small holes in it. Small molecules can pass through, but larger ones cant. We say it is selectively permeable . Selectively permeable membrane ???
    9. 9. Water concentration gradient In osmosis water moves both ways to balance up the concentrations. The overall (net) movement is to the area of low water concentration. High Water Concentration, few molecules of solute. Dilute solution Low Water Concentration, many molecules of solute. Concentrated solution Water molecule Solute molecule Key: Water movement
    10. 10. Osmosis in action http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html Have a look at this video and answer the questions on the next slide:
    11. 11. <ul><li>1 Osmosis is best defined as the movement of </li></ul><ul><li>A) molecules from an area of high concentration to an area of lower concentration. </li></ul><ul><li>B) molecules from an area of low concentration to an area of higher concentration. </li></ul><ul><li>C) water molecules across a membrane from an area of low water to an area of higher concentration. </li></ul><ul><li>D) water molecules across a membrane from an area of high water concentration to an area of lower concentration. </li></ul><ul><li>E) water molecules inside a container. </li></ul><ul><li>2 Which of the following will pass through a cell membrane most easily? </li></ul><ul><li>A) small polar molecules </li></ul><ul><li>B) small nonpolar molecules </li></ul><ul><li>C) large polar molecules </li></ul><ul><li>D) large nonpolar molecules </li></ul><ul><li>E) large neutral molecules </li></ul><ul><li>3 A red blood cell placed in a hypertonic medium will </li></ul><ul><li>A) expand. </li></ul><ul><li>B) burst. </li></ul><ul><li>C) shrink. </li></ul><ul><li>D) have no change in shape. </li></ul><ul><li>E) become a white blood cell. </li></ul><ul><li>4 A 5% urea solution is hypotonic to a 10% urea solution. </li></ul><ul><li>A) True B) False </li></ul><ul><li>If a cell is placed in an isotonic medium, there will be no net movement of water. </li></ul><ul><li>A) True B) False </li></ul>
    12. 12. Now let´s go outside and act it out! <ul><li>Nominate some sugar molecules </li></ul><ul><li>Everyone else is a water molecule </li></ul><ul><li>Draw a dashed line down the middle of the playground with chalk (your selectively permeable membrane!) </li></ul><ul><li>Arrange your water molecules either side of the membrane </li></ul><ul><li>Add your sugar molecules to one side and see if equilibrium can be restored by water moving in the right direction! </li></ul><ul><li>What happens if you remove some of the water molecules? </li></ul>