Explain what happens to a plant cell when it is placed in a concentrated sugar solution.

AQA GCSE Biology (8461) — 4.1.3 Transport in cells · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A student places a piece of plant tissue into a concentrated sugar solution and observes the cells after 30 minutes.

Model answer (4 marks)

Water moves out of the cell by osmosis.
The water moves from the dilute solution inside the cell (vacuole) to the concentrated solution outside the cell through the partially permeable membrane.
The vacuole and cytoplasm shrink.
The cell becomes plasmolysed – the cell membrane pulls away from the cell wall.

Examiner tips

  • Use the word "osmosis" to show understanding of the driving force.
  • Explain the direction of water flow (inside to outside).
  • Mention the vacuole/cytoplasm shrinking and plasmolysis to cover all marks.

Common mistakes

  • Confusing the direction of water movement – saying it moves into the cell.
  • Forgetting to mention plasmolysis or the membrane pulling away from the wall.

Mark scheme (4 marks)

  1. Water moves out of the cell (by osmosis)
  2. Water moves from a dilute solution (inside the cell/vacuole) to a concentrated solution (outside the cell) through a partially permeable membrane
  3. The vacuole / cytoplasm shrinks
  4. The cell becomes plasmolysed / the cell membrane pulls away from the cell wall

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