3. Diffusion and Osmosis



  • the net movement of particles from and area of higher concentration to lower concentration.
  • molecules will diffuse both ways, but net movement will be to the lower concentration
  • this continues until equilibrium is reached
  • concentration gradient= the path from high concentration to lower concentration
  • particles diffuse down a concentration gradient
  • it's passive- no energy/ATP is required
  • this occurs across plasma membranes


Factors affecting the rate of Diffusion

  • concentration gradient- the higher it is the higher the rate
  • thickness of exchange surface- thinner (shorter distance), the faster the rate
  • surface area- larger the surface area, the faster the rate
  • temperature- the warmer it is, the faster the rate of diffusion because the partices have more kinetic energy so move faster



  • the diffusion of water molecules across


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