Required Practical 3: Effects of Osmosis on Plant Tissue

• What should you be able to describe by the end of the video?

  How to investigate osmosis on plant tissue
• What is osmosis?

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

  Water moves into the cell, causing expansion
• What happens to plant cells in a concentrated solution?

  Water moves out, causing the cell to shrink
• What is the typical vegetable used to investigate osmosis?

  • Potato
  • Beetroot
  • Parsnip
• What should you do first when preparing potato cylinders?

  Peel the potato
• Why do we use a cork board to produce potato cylinders?

  To ensure all cylinders are the same diameter
• What is the recommended length for potato cylinders?

  About three centimeters
• Why is it important to measure the length and mass of potato cylinders?

  To assess the effect of osmosis accurately
• How much of a 0.5 molar sugar solution is added to the first test tube?

  10 centimeters cubed
• Why do we use distilled water instead of tap water?

  Distilled water has no dissolved substances
• What should you do after leaving the potato cylinders overnight?

  Gently roll them on paper towel
• Why is it important not to press on the potato cylinders when drying them?

  To avoid forcing water out of the cells
• What do you need to calculate after measuring the potato cylinders again?

  Percentage change in length and mass
• What is the formula for calculating 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 percent
• If a potato cylinder has a starting mass of 1.32 grams and decreases by 0.19 grams, what is the percentage change?

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

  • In water, potato gains mass
  • In concentrated sugar solution, potato loses mass
  • Line crosses x-axis where no osmosis occurs
• What does it mean when the graph crosses the x-axis?

  No change in mass occurs at that concentration
• What is the approximate concentration inside the potato cell?

  The concentration where the graph crosses x-axis
• What should you learn for the exam regarding this practical?

  • Details of investigating osmosis
  • How to calculate percentage change