diffusion biology 2 aqa

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  • Diffusion
    • gradual movement of particles from a high to low concentration.
      • (spread out)
    • happens in both solutions and gases
      • the particles are free to move about randomly.
    • The bigger the difference in concentration the faster the diffusion rate.
    • cell membranes
      • they hold the cell together but let stuff in and out as well.
      • dissolved substances can move in and out of cells by diffusion.
      • only very small molecules can diffuse through cell membranes - like oxygen, glucose, amino acids and water.
        • big molecules like starch and protein cant fit through the membrane.
      • if there are a lot more particles on one side of the membrane, there is a net movement from that side.
        • the particles are free to move about randomly.


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