Cell Movement

• Diffusion is the process in which a substance moves from an area of high concentration to an area of low concentration
• Osmosis is the movement of water molecules from a dilute solution to a concentrated solution through a partially permeable membrane
• Active transport is the movement of particles against a concentration gradient using energy from respiration
• Factors that can affect the rate of diffusion are:

  temperature

  concentration gradient

  surface area to volume ratio

  diffusion distance
• To speed up the process of diffusion you can:

  increase the temperature

  increase the concentration gradient

  increase the surface area

  decrease the diffusion distance
• Investigating diffusion in a non living system:

  • make some agar jelly cubes with phenolphthalein and some dilute sodium hydroxide
  • Put some dilute hydrochloric acid in a beaker and add the jelly cubes
  • after a period of time the acid will diffuse into the cubes and neutralise the sodium hydroxide, turning the pink phenolphthalein colourless
• Investigating osmosis in a living system:

  • cut a potato into identical cylinders and place them in beakers with different concentrations of sugar solution in them. one should be pure water and the other highly concentrated
  • measure the lengths before and after putting the cylinders in the beakers, and after half an hour, make a results table
  • if the cylinders have drawn in water through osmosis, they will be longer, but if they have had water drawn out through osmosis, they will be shorter in length