required practical 3: effects of osmosis on plant tissue

• Osmosis


  Diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Plant cells placed in water


  Water moves into the cell by osmosis, causing the cell to expand
• Plant cells placed in concentrated solution


  Water moves out of the plant cell by osmosis, causing the cell to shrink
• Investigating the effect of osmosis on plant tissue

  1. Peel potato

  2. Use cork board to produce potato cylinders of same diameter

  3. Trim cylinders to same length (around 3cm)

  4. Measure length and mass of each cylinder

  5. Place cylinders in test tubes with different solutions (0.5M sugar, 2.5M sugar, distilled water)

  6. Leave overnight to allow osmosis

  7. Remove cylinders, gently roll on paper towel to remove surface moisture

  8. Measure length and mass of cylinders again
• Percentage change


  Calculated as: (Change in value / Original value) x 100
• Calculating percentage change


  • Potato cylinder starting mass 1.56g, increases by 0.25g - Percentage change = (0.25 / 1.56) x 100 = +16.03%
  • Potato cylinder starting mass 1.32g, decreases by 0.19g - Percentage change = (-0.19 / 1.32) x 100 = -14.39%
• Concentration of sugar solution


  Affects percentage change in mass/length of potato cylinder
• Where the line on the graph crosses the x-axis, there is no change in mass as the concentration outside the cell is the same as the concentration inside