In osmosis, what happens to a cell placed in a hypertonic solution?

• A. Water enters cell, causing swelling
• B. Water leaves cell, causing shrinkage
• C. No net water movement
• D. Water leaves the cell, causing shrinkage (crenation in animals; plasmolysis in plant cells)

Answer: (D)

In osmosis, water moves across a semipermeable membrane toward the side with higher solute concentration. When the outside solution is hypertonic, its solute concentration is higher than inside the cell, so water leaves the cell to balance the concentrations. As water exits, the cell shrinks; in animal cells this is called crenation, while in plant cells the plasma membrane may pull away from the cell wall, a process known as plasmolysis. If water were moving into the cell, that would describe a hypotonic environment, not a hypertonic one. If the solution were isotonic, there would be no net water movement.