A Levels Biology (9700)•9700/11/M/J/25

Explanation
Plasmolysis in hypertonic solution
Steps:
- Observe plasmolysis: cytoplasm shrinks from cell wall, indicating water loss from cells.
- Water exits cells when external solution has lower (more negative) water potential than cytoplasm, causing shrinkage.
- Statement 1 correct: solution S is hypertonic, with more negative ψ than cytoplasm.
- Statement 2 incorrect: cell wall prevents bursting in hypotonic conditions (turgor), not relevant here.
- Statement 3 incomplete but describes plasmolysis gap, not a conclusion about cause.
Why B is correct:
- Plasmolysis confirms hypertonic solution (more negative ψ outside), validating only statement 1 per osmosis principles.
Why the others are wrong:
- A includes 3, but 3 is observational, not a conclusion on cause.
- C includes 2, but cell wall supports against bursting in hypotonic, not hypertonic conditions.
- D includes only 2, which misapplies cell wall role.
Final answer: B
Topic: Movement into and out of cells
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