Rate - simple

• Briefly, what does the rate of simple diffusion depend on?


  • Concentration gradient
  • Thickness of exchange surface
  • Surface area
• How does simple diffusion depend on the concentration gradient?

  The higher it is = faster the rate of diffusion

  • As diffusion takes place, the difference in conc between the 2 sides of the membrane decreases until it reaches an equilibrium (conc on both sides is equal)
  • = diffusion slows down over time
• How does rate of diffusion depend on thickness of exchange surface?

  Thinner the exchange surface (ie shorter distance the particles have to travel) = faster rate of diffusion
• How does rate of diffusion depend upon the surface area?

  Larger the surface area = faster rate of diffusion
• what are internal cell membranes?

  membranes surrounding organelles
• what do microvilli do?

  increase the surface area for faster diffusion
• Give examples of cells that have microvilli?

  Epithelial cells in the small intestine
• What are microvilli?

  Projections formed by the cell-surface membrane folding up on itself
• What do microvilli give the cell?

  A larger surface area
• What gives some cells a larger surface area?

  Microvilli
• What does a larger surface area mean?

  More particles can be exchanged in the same amount of time - increasing rate of diffusion