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Diffusion osmosis active transport

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For IGCSE O-level Biology students
Chapter 3

Publicado en: Educación
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Diffusion osmosis active transport

  1. 1. MOVEMENT OF MOLECULES Do they ever stop moving?!!
  2. 2. DIFFUSION  All molecules move about. In gaseous state, they are widespread and with weak bonds holding them together. In liquid state, they are closer with stronger bonds holding them together. In solids they are very close and could only vibrate in their place.
  3. 3. NOW PUT UP YOUR HAND AS SOON AS YOU CAN DETECT THE SMELL OF THE AIR FRESHENER.
  4. 4. WHAT DO YOU NOTICE?  Who were the first to detect the smell?  Who were last to detect the smell?  Why isn’t there anyone who did not detect the smell?  Explain how you could smell the scent although you are far away from the air freshener.  What if we opened the door or window? Would others outside be able to smell the scent?
  5. 5. WHAT WOULD HAPPEN TO A LUMP OF SUGAR PLACED IN A CUP OF WATER?
  6. 6. WHAT WOULD MAKE MOLECULES MOVE/SPREAD OUT FASTER OR SLOWER?  Temperature  Stirring/ air currents  Number of molecules  Surface area  Distance/ thickness of membrane  Difference between molecule concentration in both areas
  7. 7. DIFFUSION Is the movement of molecules from a region of high concentration to a region of low concentration down a concentration gradient.
  8. 8. OSMOSIS  A special type of diffusion involving the movement of water molecules only, through a partially permeable membrane.  Partially permeable membrane is a membrane with small holes that can allow only small molecules to pass through.
  9. 9. NOW I NEED FOUR VOLUNTEERS!
  10. 10. OSMOSIS Is the movement of water molecules from a dilute solution (high water potential) to a concentrated solution (low water potential) through a partially permeable membrane.  A cell membrane is a partially permeable membrane.
  11. 11. WHAT HAPPENS TO ANIMAL CELLS IF THEY WERE PLACED IN A SOLUTION OF A DIFFERENT CONCENTRATION THAN OF THEIR CYTOPLASM?
  12. 12. WHAT ABOUT PLANT CELLS?
  13. 13. OSMOSIS IN PLANT CELLS.  Water enters a plant cell, the water molecules put pressure on the walls. The rigid cell wall will prevent the cell from bursting. This plant cell is said to be turgid.  This keeps the plant firm.
  14. 14. OSMOSIS IN PLANT CELLS  When water leaves the plant cell the elastic cell membrane shrinks, while the rigid cell wall keeps the shape of the cell fixed. This plant cell is said to be plasmolysed.
  15. 15.  ACTIVE TRANSPORT  In some situations, there is a need to move molecules from a region of low concentration to a region of high concentration.  A root hair cell needs to take in minerals from the soil, even if the concentration in the soil is lower than that in the cells. 10

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