1. particles
   1. random motion
      1. achieve even spacing
2. Diffusion
   1. passive movement of particles from an area of high concentration to an area of low concentration
   2. gradual movement : lots to fewer
   3. natural tendency to spread out
   4. liquids & gases
      1. particles free to move
      2. different gasses diffuse
         1. smell
   5. across membranes
      1. small molecules
         1. diffuse
         2. glucose
         3. amino acids
         4. water
         5. oxygen
      2. membrane
         1. holds cell together
         2. allow stuff in & out
            1. diffusion
            2. osmosis
            3. high to low concentration
            4. go both ways through membrane
            5. net overall flow high to low
         3. stops big molecules
            1. starch
            2. protein
   6. rate of diffusion
      1. distance
         1. less = quicker
      2. concentration difference (gradient)
         1. more particle on one side = quicker
      3. surface area
         1. greater = faster
3. Osmosis
   1. movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration
   2. partially permeable membrane
      1. very small holes
      2. allows tiny molecules through
         1. water
      3. large molecules stopped
         1. sucrose
   3. water
      1. pass both ways
         1. random
      2. steady net flow
         1. into region of fewer water molecules
         2. evens up water concentration
         3. into stronger sugar solution
            1. gets more dilute
   4. type of diffusion
   5. water in and out of cells
      1. Tissue fluid
         1. surrounds cells
         2. contains
            1. water
            2. glucose
            3. dissolved stuff
         3. squeezed out of blood capillaries
         4. cell / tissue fluid concentrations
            1. different
            2. outside more dilute
            3. cell short on water
            4. water into cell
            5. cell dilute (lots water)
            6. water drawn out of cell