transporting substances

• Active transport is when substances are transported against the concentration gradient from a low concentration to a high concentration, so the process requires a lot of energy.
• Diffusion is when substances move from a high concentration to a low concentration.
• Osmosis is when water molecules move from a high concentration to a low concentration across a semi-permeable membrane.
• Osmosis potato experiment:

  1. Prepare a range of solutions with different concentrations of salt/sugar in boiling tubes.
  2. Measure mass of potato cylinder and place it in a boiling tube.
  3. Remove potato strip after 20 minutes, dry carefully, measure and record mass.
  4. Repeat for each concentration.
• Potato experiment shows that the cylinder will decrease or increase in mass if they lose or gain water by osmosis.