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CAIE IGCSE Biology 3.2 Osmosis Questions

Practise applying osmosis and water-potential gradients to animal cells, plant tissues and investigation data, including turgor, plasmolysis and percentage change.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • Explain water's role as a solvent for digested molecules and other dissolved substances, supporting transport, digestion and excretion.
  • Define osmosis as the net movement of water molecules through a partially permeable membrane from higher to lower water potential, including numerical comparisons.
  • Predict and explain water gain or loss in plant cells, animal cells and tissues, including turgid, flaccid and plasmolysed states.
  • Interpret osmosis investigations using dialysis tubing, potato or tissue data, percentage change and the zero-change point.
  • Explain turgor pressure acting against cell walls to support young plants, and distinguish it from transpiration pull or substance transport.
  • Apply water-potential gradients to root uptake and organism water balance, including the effect of nitrate-ion uptake on continued osmotic water entry.

Covered syllabus points

3.2.1—Water as a solvent3.2.2—Water diffuses through partially3.2.3—Osmosis through cell membranes3.2.4—Osmosis using materials such3.2.5—Effects on plant tissues of immersing3.2.6—Plants are supported by the pressure3.2.7—Osmosis as the net movement of water3.2.8—Effects on plant cells of immersing3.2.9—Importance of water potential

Question 1

[Maximum number: 1]

Digestive enzymes catalyse the breakdown of large insoluble molecules.

State the name of the substance that is the solvent for most molecules that have been digested by enzymes.

Question 2

[Maximum number: 1]

Which molecule crosses a partially permeable membrane during osmosis?

A

carbon dioxide

B

oxygen

C

urea

D

water

Question 3

[Maximum number: 1]

Fig. 5.1 is a diagram of a plant root hair cell.
Key
× nitrate ion
- water molecule

Fig. 5.1

Fig. 5.1

State the name of the process that moves water molecules into root hair cells.

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