Syllabus Edition

First teaching 2023

First exams 2025

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Water Potential (SL IB Biology)

Exam Questions

22 mins6 questions
11 mark

The diagram below shows red blood cells that have been bathed in solutions of different solute concentration.

q2-1-3-cell-membrane-medium-ib-hl-biology

Which row of the table correctly describes the three solutions that these red blood cells have been bathed in?

  I II III
A. Isotonic Hypotonic Isotonic
B. Isotonic Hypertonic Hypotonic
C. Isotonic Hypotonic Hypertonic
D. Hypertonic Hypotonic Isotonic

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    21 mark

    A student places an animal cell and a plant cell into distilled water and notes the following observations.

           Animal cell: swells and then bursts.

          Plant cell: swells.

    What is the reason for this difference?

    • Plant cell surface membranes are partially permeable

    • Animal cells have no vacuole

    • Animal cells have no cell wall

    • Plant cell walls are freely permeable

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    1
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    1 mark

    An experiment to calculate the water potential of potato cells was performed using the following protocol:

    1. Dice potato into 1cm3 cubes.
    2. Add potato cubes to 6 test tubes, each containing solution with a different sucrose concentration.
    3. Wait 12 hours.
    4. Weigh the cubes from each test tube and plot a graph. 

    The mean mass of the potato cubes was 2.50 g before being added to the solution, and the graph shows the masses of the potato cubes after the experiment. 1-3-h-q4-paper-1

    Which concentration of sucrose matches the water potential of the potato cells?

    • 0.00 mol dm-3

    • 0.12 mol dm-3

    • 0.31 mol dm-3

    • 0.66 mol dm-3

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