Movement of particles (Diffusion, Osmosis, Active Transport)

• Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
• Factors affecting the rate of diffusion:

  Size of the particles, air flow, temperature, concentration of particles
• Osmosis


  The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Dilute solution


  • Contains a high concentration of water
  • Contains a low concentration of solute (e.g. sugar)
• Concentrated solution


  • Contains a low concentration of water
  • Contains a high concentration of solute (e.g. sugar)
• Animal cell in water


  Water moves into the cell by osmosis, causing the cell to expand and potentially burst
• Animal cell in concentrated solution


  Water moves out of the cell by osmosis, causing the cell to shrink
• Plant cell in water

  Water moves into the cell by osmosis, causing the cell to become turgid (swollen)
• Plant cell in concentrated solution

  Water moves out of the cell by osmosis, causing the cell to become flaccid (shrunken)
• The cell wall prevents the plant cell from bursting when water moves in by osmosis
• hypotonic - water moves into the cell, cell swells up, cell bursts
• isotonic - water enters and exits the cells
• hypertonic - water moves out of the cell and the cell shrinks
• if the concentration of solutes in the solution outside the cell is higher than the internal concentration, the solution is hypertonic to the cell


  if the concentration of solutes in the solution outside the cell is lower than the internal concentration, the solution is hypotonic to the cell
• active transport - the movement of molecules from a low concentration to a high concentration through a membrane (going against the concentration gradient)

  active transport requires energy