Which of the following can cause shrinkage of living cells?

1. Analyze the question The question asks which solution makes living cells shrink. This is about osmosis and the movement of water across a cell membrane.

2. Explain the concept Osmosis is the movement of water from a region of higher water concentration to one of lower water concentration through a semi-permeable membrane. The effect on a cell depends on the concentration of the surrounding solution compared with the cell's cytoplasm:

| Solution type | Solute concentration outside vs. inside | Water movement | Effect on cell | |---|---|---|---| | Hypotonic | Lower outside | Into the cell | Swells (animal cells may burst; plant cells become turgid) | | Isotonic | Equal | No net movement | No change | | Hypertonic | Higher outside | Out of the cell | Shrinks (crenation in animal cells, plasmolysis in plant cells) |

3. Solution

• A. Hypotonic solution: water enters the cell, so it swells. Not correct.
• B. Isotonic solution: there is no net water movement, so the cell stays the same. Not correct.
• C. Deionized water: this is pure water with no solutes. It is extremely hypotonic to the cell, so water rushes in and the cell swells. Not correct.
• D. Hypertonic solution: the outside has more solutes, so water leaves the cell by osmosis and the cell shrinks. Correct.

4. Answer The correct option is D. Hypertonic solution.

5. Exam tip Remember: "Hyper = shrink". A hypertonic solution has more solute outside, so water goes out. For hypotonic, think "hypo = hippo", which is big and swollen, so the cell swells. In plant cells, the shrinking in a hypertonic solution is called plasmolysis, a term JAMB often asks about.