cell biology : required practicle - osmosis

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

  How to investigate the effect of osmosis on plant tissue
• What is osmosis?

  The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• What happens to plant cells when they are placed in water?

  Water moves into the cell by osmosis, causing the cell to expand
• What occurs when a plant cell is placed in a concentrated solution?

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

  • Potato
  • Other vegetables: beetroot, parsnip
• Why do we peel the potato before the experiment?

  Because the potato skin can affect osmosis
• How do we ensure all potato cylinders are the same diameter?

  By using a cork borer to produce the cylinders
• What is the recommended length for the potato cylinders?

  Approximately three centimeters
• Why is it important to measure the length and mass of each potato cylinder?

  To assess the effect of osmosis on the cylinders
• What volume of 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 in the experiment?

  Because distilled water contains no dissolved substances that could affect osmosis
• What should be done after leaving the potato cylinders overnight?

  Gently roll them on paper towel to remove surface moisture
• Why is it important not to press on the potato cylinders when removing surface moisture?

  To avoid forcing water out of the cells
• What do we need to calculate after measuring the length and mass of the cylinders again?

  The 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 increase?

  16.03%
• If a potato cylinder has a starting mass of 1.32 grams and decreases by 0.19 grams, what is the percentage decrease?

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

  • In water, potato cylinders gain mass (water moves in)
  • In concentrated sugar solution, cylinders lose mass (water moves out)
  • The x-axis crossing indicates no change in mass (equal concentration inside and outside)
• What does it mean when the line crosses the x-axis on the graph?

  It indicates no overall osmosis takes place
• Where can students find more questions on this required practical?

  In the vision workbook linked in the video
• What should you be able to do after watching the video?

  Describe how to investigate the effect of osmosis on plant tissue and calculate percentage change