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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.

Question 4

[Maximum number: 1]

The diagram shows apparatus which can be used to demonstrate osmosis.

Figure for Question 4 — CAIE IGCSE Biology

After one hour, what would happen to the liquid levels in the glass tubes?

liquid level in

tube 1

liquid level in

tube 2

falls

falls

falls

rises

rises

falls

rises

rises

Question 5

[Maximum number: 1]

Some students investigated osmosis in raw potato sticks.

The students measured the mass of four of the potato sticks using an electronic balance.

Fig. 4.1 shows an electronic balance.

Fig. 4.1

Fig. 4.1

The students left each potato stick in one of four different liquids for 5 hours:
- distilled water
- 0.1 mol per dm3\mathrm{dm}^{3} sodium chloride solution
- 0.5 mol per dm3\mathrm{dm}^{3} sodium chloride solution
- 1.0 mol per dm3\mathrm{dm}^{3} sodium chloride solution.

After 5 hours they measured the mass again and calculated the change in mass.

Predict which of the liquids would cause the largest decrease in mass of a potato stick.

Question 6

[Maximum number: 1]

Which statement about the role of the pressure of water in supporting plants is correct?

A

The pressure of water inside the cells presses inwards on the cell wall.

B

The pressure of water outside the cells presses inwards on the cell wall.

C

The pressure of water inside the cells presses outwards on the cell wall.

D

The pressure of water outside the cells presses outwards on the cell wall.

Question 7

[Maximum number: 3]

Some students investigated osmosis in raw potato sticks.

Define the term osmosis.

Question 8

[Maximum number: 3]

A student observed cells from a plant that had wilted.

State and explain the expected appearance of the cells.

Question 9

[Maximum number: 1]

Fig. 2.1 is a photomicrograph of the end of a plant root.

Fig. 2.1

Fig. 2.1

Fig. 2.2 shows the results of a study on the rate of uptake of nitrate ions at different points along the root shown in Fig. 2.1.
rate of nitrate ion uptake / pmol per cm2\mathrm{cm}^{2} per s

Fig. 2.2

Fig. 2.2

Explain why the uptake of ions, such as nitrate, is important for the uptake of water in roots.

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