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  • Diffusion
    • Diffusion is the spreading out of particles from an area of HIGH CONCENTRATION to an area of LOW CONCENTRATION.
      • Diffusion happens in solutions and gases. That's because the particles in these substances are free to move about randomly. For example, the smell of perfume diffuses through the air in a room.
      • The bigger the difference in concentration, the faster the rate (speed) of diffusion.
    • Cell Membranes
      • They hold the cell together BUT they let stuff in and out as well.
      • Dissolve substances can move in and out of cells by DIFFUSION.
      • Only very SMALL molecules can diffuse through cell membranes e.g. oxygen, glucose, water and amino acids.
      • BIG molecules like starch and proteins can't fit through the membrane.
      • Just like diffusion in the air, Molecules move from where there's a HIGH CONCENTRATION to where there's a LOW CONCENTRATION.
      • They actually move BOTH ways but if there are a lot MORE molecules on one side of the membrane, there's a NET (overall) movement FROM that side.


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