Diffusion, osmosis & Active transport

• what is diffusion ?

  the net movement of particles from an area of high concentration to an area of low concentration
• does diffusion require energy ?

  no, its a passive process
• diffusion happens in both liquids and gases because the particles in these substances are free to move about randomly
• give an example of diffusion in gases ?

  water vapour molecules diffusing out of a leaf
• where is another common place other than air where diffusion occurs ?

  partially permeable cell membranes
• what is osmosis ?

  The movement of water molecules from an area of high concentration to an area of low concentration across a semi-permeable membrane.
• example of osmosis in animals and plants ?

  controlling guard cells

  reabsorption in kidneys
• high water concentration = low solute concentration

  (dilute)
• low water concentration = high solute concentration

  (concentrated)
• what is another common place osmosis can occur ?

  partially permeable cell membrane
• 3 types of osmosis in animal cells ?

  • hypertonic solution
  • isotonic solution
  • hypotonic solution
• describe the 3 different animal cells osmosis

  A) shrivelled cells

  B) net movement of water out

  C) cells have high water concentration compared to solutio

  D) normal cells

  E) concentration equal between cells and solution

  F) no net movement of water

  G) cells swelling

  H) net movement of water in

  I) cells have a lower concentration compared to solution

  
• what is active transport ?

  Movement of molecules across a cell membrane that requires energy.
• where does the energy come from in active transport ?

  respiration
• what do active transport of ions in a root hair cell increase ?

  • solute concentration
  • osmosis in cell
• 2 differences between diffusion and active transport ?

  • active transport requires energy whereas diffusion doesnt
  • diffusion goes from an area of high concentration to an area of low concentration but active transport goes from an area of low concentration to high concentration
• besides energy what does active transport also require which diffusion doesnt ?

  protein carriers
• what are the 4 factors affecting the movement of substances ?

  • surface area to volume ratio
  • distance
  • temperature
  • concentration gradient
• the rate of diffusion, osmosis and active transport is higher in cells with a larger surface area to volume ratio