Transport Revision

• Diffusion is the movement of particles from an area of high concentration to an area of low concentration
• A high concentration gradient means a big difference between the number of particles on each side of the diffusion pathway
• A low concentration gradient means a small difference between the number of particles on each side of the diffusion pathway
• What is a concentration gradient?

  A concentration gradient is the difference in concentration between one area and another. 

  Diffusion happens down a concentration gradient from an area of high concentration to an area of low concentration.
• diffusion

  movement of molecules from high concentration to low concentration
• osmosis

  movement of solvent (water) across a semipermeable membrane from high to low solvent concentration
• Osmosis is exactly the same as diffusion. The particles still move DOWN a concentration gradient from a high concentration (lots of particles) to a low concentration gradient (few particles)

  However, osmosis is what we call diffusion when it is ONLY water that is moving from high to low concentration.