Describe what happens to a plant cell placed in a hypertonic solution.

Answer

Water leaves the cell by osmosis, the vacuole shrinks and the cell becomes flaccid and then plasmolysed — the membrane pulls away from the cell wall.

Explanation

Step 1 — Compare the two solutions

A hypertonic solution has a higher solute concentration than the cell sap, which means a lower (more negative) water potential outside the cell than inside.

Step 2 — Work out the direction of osmosis

Water moves down the water-potential gradient, from high to low:

inside (higher Ψ) → outside (lower Ψ)

So water leaves the cell through the partially permeable membrane.

Step 3 — Follow what that does to the cell

stage	what happens
Water leaves the vacuole	The vacuole shrinks and turgor pressure falls
Cell becomes flaccid	The contents no longer press on the wall
Plasmolysis	The membrane pulls away from the cell wall

Step 4 — State the outcome

The cell is plasmolysed. The cellulose cell wall is rigid, so the cell keeps its shape rather than shrivelling — this is why a plant cell behaves differently from an animal cell, which would simply crenate.

Check

If the cell is returned to a hypotonic solution before the damage is permanent, water re-enters and the cell becomes turgid again — the process is reversible up to a point.

Skills You Achive

cell biology osmosis