Which of the following can cause shrinkage of living cells?

Step 1: Analyze the question The question asks which solution makes living cells shrink. Shrinkage means the cell is losing water.

Step 2: The concept (osmosis) Osmosis is the movement of water from a region of higher water concentration (lower solute concentration) to a region of lower water concentration (higher solute concentration) through a selectively permeable membrane.

Three types of external solutions:

• Hypotonic: lower solute concentration than the cell. Water moves into the cell, so it swells and may burst (animal cells lyse; plant cells become turgid).
• Isotonic: same solute concentration as the cell. There is no net movement of water, so the cell stays the same size.
• Hypertonic: higher solute concentration than the cell. Water moves out of the cell, so it shrinks. In animal cells this is called crenation, and in plant cells it is plasmolysis.

Step 3: Evaluate the options

• A. Deionized water: This is pure water with no dissolved solutes, so it is strongly hypotonic. Water enters the cell, causing swelling. ✗
• B. Hypotonic solution: Water enters the cell, causing swelling. ✗
• C. Isotonic solution: There is no net water movement. ✗
• D. Hypertonic solution: Water leaves the cell, causing shrinkage. ✓

Answer: D. Hypertonic solution

Exam tip: Remember "Hyper = shrinks". Hypertonic has more solute outside, so water rushes out. You can also remember "Hypo = Hippo", because the cell swells up like a hippo. Salting meat or slugs shrivelling when salt is poured on them are everyday examples of hypertonic effects.