Effects of Osmosis on Plant Tissue

• What is osmosis?

  Diffusion of water through a membrane
• What happens to plant cells when placed in water?

  Water moves in, causing cells to expand
• What occurs when plant cells are placed in a concentrated solution?

  Water moves out, causing cells to shrink
• What is the procedure to investigate osmosis using potatoes?

  1. Peel the potato to avoid skin effects.
  2. Use a cork board to cut uniform cylinders.
  3. Trim cylinders to about 3 cm in length.
  4. Measure length and mass of each cylinder.
  5. Place cylinders in test tubes with different sugar solutions.
  6. Leave overnight for osmosis to occur.
  7. Remove and roll on paper towel to remove surface moisture.
  8. Measure length and mass again.
• What is the purpose of using distilled water in the experiment?

  It contains no dissolved substances
• Why is it important not to press on the potato cylinders after removing them?

  To avoid forcing water out of the cells
• What equation is used to calculate percentage change?

  Percentage change = (change in value / original value) × 100
• If a potato cylinder has a starting mass of 1.56 grams and increases by 0.25 grams, what is the percentage change?

  +16.03%
• What is the percentage change if a potato cylinder starts at 1.32 grams and decreases by 0.19 grams?

  -14.39%
• What does the graph of percentage changes in mass or length against sugar solution concentration show?

  • In water, potato gains mass (osmosis in).
  • In concentrated sugar solution, potato loses mass (osmosis out).
  • The x-axis crossing indicates no mass change.
  • This point shows equal concentration inside and outside the cell.
• What is the significance of the concentration where the graph crosses the x-axis?

  It indicates no overall osmosis occurs