2.12 understand definitions of diffusion, osmosis and active transport


  • The overall movement of particles from an area of high concentration to an area of low concentration till an equal concentration has been reached
  • Caused by a random movement of particles in fluids
  • Diffusion is a passive process – it does NOT require energy
  • Diffusion rates can be altered by concentration, temperature and available surface area


  • The movement of water molecules from a region of high water concentration to a low water concentration across a partially permeable membrane
  • Does not require energy
  • Concentration of WATER molecules

Active Transport

  • The molecules being moved from an area of low concentration to a high concentration across a selectively permeable membrane
  • Active transport is an active process – it requires energy produced by cellular respiration

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