Passive Transport

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Passive Transport
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Diffusion

• The net movement of molecules from a region where
  they are in high concentration to a region where
  they are in low concentration.
• Molecules are in constant, random (Brownian)
  motion
• As they collide with each other and with the
  sides of their container, they rebound, changing
  speed and direction( What affects the rate of
  diffusion?)

• http//bio.winona.edu/berg/ANIMTNS/Directry.htm

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• Diffusion of particles continues down the
  concentration gradient (see text) until the
  concentration is the same in all areas of the
  container.
• The particles do not stop moving and dynamic
  equilibrium has been reached. (continuous
  movement, no overall change)

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• Many molecules can move easily through the cell
  membrane as a result of diffusion.
• Assume more molecules of one type outside the
  cell.
• There is a greater chance they will hit the cell
  membrane and move in than the same molecules in
  the cell hitting and moving out.
• As the number of molecules inside increases the
  probability of hitting and moving in the
  chances of hitting the membrane and moving out. (
  dynamic equilibrium has been reached)
• http//bio.winona.edu/berg/ANIMTNS/Directry.htm

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Osmosis

• A special type of diffusion
• The diffusion of water across a semi-permeable
  membrane
• Three terms you need to know
• Isotonic the solute concentration inside the
  cell is the same as it is outside the cell
• Hypotonic the solute concentration on one side
  of the cell is less than on the other side of the
  cell
• Hypertonic the solute concentration on one side
  of the cell is more than on the other side of the
  cell

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