Osmosis

• Diffusion is the movement of particles down a concentration gradient whereas active transport is against
• Active transport requires energy from respiration whereas diffusion doesn't
• Active transport requires a membrane protein to help move molecules whereas diffusion doesn't
• Lungs


  • Has many folded alveoli which increases its surface area
  • Alveoli are one cell thick so the diffusion distance for oxygen is shorter
  • A good blood supply maintains a high concentration gradient
• Solute

  Something that can be dissolved
• Solvent


  The liquid the solute dissolves into
• Adding salt to vegetables before cooking causes water to leave the cells
• Osmosis


  The movement of water from an area of higher water concentration to lower water concentration across a partially-permeable membrane
• Osmosis


  1. Water molecules diffuse from where there is a higher concentration of water to a lower concentration of water

  2. OR

  3. From where there is a lower concentration of solute towards where there is more solute e.g. dissolved salt or sugar

  4. This happens until the concentration is equal on either side of the semi-permeable membrane
• Osmosis


  • pure water
  • dilute solution
  • concentrated solution
• Root hair cell vacuoles contain a high concentration of salts and sugars
• If too much fertilizer is put into the soil in one go, a problem might occur
• Concentration of sugar solution (M)

  • 0 (distilled water)
  • 0.4
  • 0.8
  • 1.0
• Results table


  • Initial mass of potato (g)
  • Final mass of potato (g)
  • Change in mass (g)
  • Percentage change in mass (%)
• Isotonic solution


  Concentration of water inside the cell is the same as the outside
• Hypertonic solution


  Concentration of water outside the cell is lower than inside
• Hypotonic solution


  Concentration of water outside the cell is higher than inside
• Plasmolysed


  Concentrated solution
• Burst


  Dilute solution
• Osmosis


  1. The movement of water from an area of high water concentration to an area of low water concentration through a partially-permeable membrane

  2. The solute is too large to pass through the gaps, but water molecules are small enough

  3. Water moves to an area where there is a lower solute concentration
• Osmosis is the diffusion of water molecules from a dilute solution to a more concentrated solution, across a partially-permeable membrane
• OSMOSIS IS THE MOVEMENT OF WATER FROM AN AREA OF HIGH WATER CONCENTRATION TO AN AREA OF LOW WATER CONCENTRATION ACROSS A PARTIALLY-PERMEABLE MEMBRANE
• A partially-permeable membrane has holes in it that permit water molecules through but are too small to allow larger (solute) molecules through
• People pour salt on slugs to kill them because it causes osmosis, drawing water out of the slug's cells
• Results table


  • Concentration of sugar solution (M)
  • Initial mass of potato (g)
  • Final mass of potato (g)
  • Change in mass (g)
  • Percentage change in mass (%)
• Independent variable


  x axis
• Dependent variable


  y axis