Exchange of materials B3 1.1

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What is Osmosis?

  • Osmosis is the movement of water through a  partially permable membrane.
  • Osmosis needs no energy from the cell

  • It diffuses water from high water concentration (dilute)  to low water concentration (more concentrated).
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What is a 'Partially Permable membrane'?

  • Membranes which only let some types of particles through.
  • They let water move across them (osmosis)
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Whats the difference between 'diffusion' and 'osmo

  • Diffusion refers to the movement of any particles from a region of hight to low concentration
  • Osmosis only refers to the movement of water molecules
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Why is osmosis important in animals?

  • It helps maintain constant internal conditions, and restores balance in the cells

If a cell uses up water in chemical reactions

  • the cytoplasm becomes more concentrated and more water immediatly moves in by osmosis
  • if too much water moves in, the cell will swell and may burst

If more water is produced in a cells chemical reactions

  • The cytoplasm becomes more dilute and water leaves the cell by osmosis
  • when water moves out of the cell, theres a risk of the cytoplasm getting too concentrated, shrivel up, and can no longer survive
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Why is osmosis important in plants?

  • Plants rely on osmosis to support their stem and leaves

  • Water moves into the plant cells causing the vacuole to swell and press the cytoplasm against the cell walls

  • This builds up until no more water can enter the cell, making the plant hard and rigid.
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