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Movement of Substances (part 1): Diffusion & Osmosis

Learning Outcomes<br>Students should be able to:<br>- define diffusion and describe its role in nutrient uptake and gaseous exchange in plants and<br>humans<br>- define osmosis and describe the effects of osmosis on plant and animal tissues

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Movement of Substances (part 1): Diffusion & Osmosis

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  1. Movement of substances Chapter 3 1) Diffusion 2) Osmosis 3) Active Transport

  2. 1) Diffusion

  3. Lesson Objectives: ⚫ Define diffusion ⚫ Know what is the meaning of down a concentration gradient

  4. Diffusion ⚫ Diffusion is the net movement of ions or molecules from a region where they are in higher concentration to a region where they are in lower concentration i.e. down a concentration gradient

  5. Example of diffusion

  6. Concentration gradient Direction of movement of molecules concentration concentration difference distance

  7. Diffusion gradient ⚫ The steeper the diffusion gradient for a substance, the faster the rate of diffusion for that substance

  8. Solutions dissolves sugar + (solute) water (solvent) sugar solution (solution) + Solute: the substance that dissolves in a liquid; can be soluble or insoluble in a given solvent Solvent: a liquid which dissolves other substances

  9. Diffusion of dyes

  10. Diffusion of dyes

  11. 2) Osmosis

  12. Lesson objectives ⚫ Define osmosis ⚫ Understand the meaning of water potential ⚫ Understand meaning of isotonic, hypotonic and hypertonic solutions ⚫ Know the reaction of cells in isotonic, hypotonic and hypertonic solutions

  13. Osmosis ⚫ the movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

  14. Osmosis

  15. Water potential ⚫ Definition: Water potential is a measure of the water molecule potential for movement in a solution ⚫ measured in units of pressure (Pa, or usually kPa)

  16. Water potential ⚫ High solute content = low water potential ⚫ Low solute content = high water potential Why?

  17. Osmosis ⚫ - High solute - Low solute - High water potential - Low water potential

  18. Investigation 3.2 (pg. 27) Aim: To demonstrate osmosis (high water potential) (low water potential) (partially permeable membrane)

  19. Reverse osmosis

  20. Water potential

  21. Reverse Osmosis ⚫ partially Direction? Direction?

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