1.3.9

Required Practical - Osmosis in Plant Tissue

Test yourself

Concentrations of Salt or Sugar Solutions on Plant Tissue

The aim of this practical is to investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue using osmosis theory.

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Calculate the results

  • Using the recorded results, calculate the change in mass and percentage change.
  • To find the percentage change in mass =

    • FinalMassInitialMassInitialMass×100\dfrac{Final Mass - Initial Mass}{Initial Mass} \times 100
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Plot the results

  • Plot a graph of percentage change in mass (y-axis) against concentration of solution (x-axis).
    • The point where the curve crosses 0% indicates the isotonic concentration of the potato cells.
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Variables

  • Independent variable:
    • Concentration of salt or sugar solution (mol dm-3)
  • Dependent variable:
    • Change in mass (and length) of potato cylinders
  • Control variables:
    • Type of plant tissue, temperature, volume of solution, time left in solution, size and shape of potato pieces
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Explanation

  • In pure water (0.0M), potato gains mass → water moves into the cells by osmosis.
  • In strong solutions (1.0M), potato loses mass → water moves out of the cells.
  • The concentration where no change occurs is isotonic – equal concentration inside and outside the cells.
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Evaluation and Improvements

  • Possible errors:
    • Unequal potato size or surface area
    • Inaccurate drying before weighing
    • Evaporation of the solution
  • Improvements:
    • Use more concentration points for accuracy
    • Repeat each concentration at least 3 times and calculate a mean
    • Use a more precise balance

Jump to other topics

1Cell Biology

1.1What's in Cells?

1.2Cell Division

1.3Transport in Cells

2Organisation

2.1Principles of Organisation

2.2Enzymes

2.3Circulatory System

2.4Non-Communicable Diseases

2.5Plant Tissues, Organs & Systems

3Infection & Response

4Bioenergetics

5Homeostasis & Response

5.1Homeostasis

5.2The Human Nervous System

5.3Hormonal Coordination in Humans

5.4Plant Hormones

6Inheritance, Variation & Evolution

6.1Reproduction

6.2Variation & Evolution

6.3Genetics & Evolution

6.4Classification

7Ecology

7.1Adaptations & Interdependence

7.2Organisation of Ecosystems

7.3Biodiversity

7.4Trophic Levels

7.5Food Production

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