Biology B3 - Diffusion, osmosis and active transport.

Diffusion, osmosis and active transport.

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  • When particles spread out from a high concentration, to a low concentration.
    • This happens in the lungs (alveoli) when carbon dioxide is taken out of the body, and oxygen is taken in. The alveoli is good for diffusion because it has;
      •   A good blood supply
        • Moist lining
          • Large surface area.
    • It also happens in plant cells when water is taken up through the root hairs. The root hair cell has;
      • A large surface area
        • Contains a vacuole to help absorb water.
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  • The movement of water molecules from an area of high concentration to an area of low concentration.
    • If you have a solution of water and a sugar solution;
      • The water will diffuse into the sugar solution, but the sugar particles are too large to pass through the partially mermeable membrane.
        • After time, the sugar solution will contain more water than it has before the osmosis began.
          • Finally, equillibrium, equal amounts of water flowing in each direction.

    • Osmosis also makes plants swell up and become turgid (full of water, swollen).
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Active Transport

  • The movement of molecules against the concentration gradient, (from low to high concentration).
    • When roots hairs take up minerals from the soil, they use active transport. (Diffusion takes up water from the soil, so don't get them confused!)
    • Active transport occurs when the glucose, amino acids, fatty acids etc.. in the gut are taken into the blood.
    • Active transport occurs in the kidneys when the water and ions are reabsorbed back into the blood.
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its permeable not 'mermeable'. get it right ;) haha ***

Pierre Fleet


good notes! just to add on the first slide... other adaptations of the alveoli include: thin walls to make diffusion easier, spherical shape to give a relatively large surface area :) :)

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