simple diffusion

• the net movement of particles from a region of higher concentration to a region of lower concentration
• in simple diffusion particles move down the concentration gradient
• the plasma membrane has tiny pores to allow small molecules to diffuse through
• rate of diffusion is affected by:

  1. concentration gradient
  2. surface area
  3. thickness of exchange surface
• rate of diffusion: concentration gradient

  • bigger difference in concentration
  • steeper concentration gradient
  • faster rate of diffusion
• rate of diffusion: surface area

  • larger surface area
  • faster rate of diffusion
• rate of diffusion: thickness of exchange surface

  • thinner exchange surface
  • smaller diffusion pathway
  • faster rate of diffusion
• Fick's law shows the relationship between the 3 factors affecting the rate of diffusion
• Fick's law:

  rate of diffusion ∝ (surface area x conc. difference)/distance between the 2 areas
• smaller(gases), fat soluble and non-polar molecules diffuse quicker