Osmosis and Plant Transport

Mind map covering whole chapter on Osmosis and Plant Transport. CCEA revised Unit 2 chapter 8.

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  • Created by: Abigail
  • Created on: 13-06-13 14:51
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  • Osmosis and Plant Transport
    • Definitions
      • Selectively permeable: Allows some substances to pass through but prevents the movement of others
      • Diffusion: the random movement of a substance from where it is in high concentration to where the concentration is lower
      • Osmosis: A special type of diffusion involving the movement of water molecules through a selectively permeable membrane
    • Osmosis
      • Water moves from the weaker (more dilute solution to the stronger (more concentrated solution through a selectively permeable membrane
      • In osmosis water molecules move but other larger molecules such as sugar cannot move through the selectively permeable membrane
      • A concentration gradient exists across a selectively permeable membrane
        • Concentration gradient: difference in concentrations on either side
    • Osmosis in plant cells
      • When water moves into the plant cell, the vacuole increases in size, pushing the cell membrane against the cell wall
      • Cell wall stretches slightly-cell becomes turgid
      • Cell wall prevents too much water from entering the cell and causing it to burst
      • When plants do not receive enough water they cannot remain turgid and wilting occurs - they become flaccid
      • If a cell loses to much water plasmolysis occurs. So much water leaves the cell that the cell contents shrivel, pulling the cell membrane away from the cell wall
    • Osmosis in animal cells
      • Animal cells do not have a cell wall so water entering and leaving the cell cannot be controlled
      • If too much water enters the cell through  osmosis,  it fills with so much water that it bursts
      • If the cell is in e.g a strong sugar solution, so much water will leave the cell that it shrivels up- crenation
    • Transpiration
      • Transpiration is the loss of water by evaporatio
      • The evaporation of water takes place mainly in plant  leaves from the spongy mesophyll cells, through the air spaces and out of the stomata
      • Main functions of water in the plant
        • transpiration
        • photosynthesis
        • transport
        • support
      • measuring water uptake using potometer
        • average rate of movement=distance moved by bubble/time taken
      • Environmental Factors affecting transpiration
        • temperature
        • wind speed
        • humidity
        • light




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