Having greater concentration of solute inside than the solution outside. Cell shrinks. What is this condition called?

• A. Hypertonic
• B. Hypotonic
• C. Isotonic
• D. Equilibrium

Answer: (A)

The main idea is tonicity and osmosis: water moves toward the area of higher solute concentration. If the solution surrounding a cell has a higher solute concentration than the cell’s interior, the outside is hypertonic to the cell. Water exits the cell in an attempt to balance solute levels, causing the cell to shrink (crenate). So, the situation described—cell shrinkage due to a more concentrated external environment—is best called hypertonic.

For completeness: isotonic means solute concentrations are equal inside and outside, so there’s no net water movement; hypotonic means the outside has lower solute concentration, so water would enter the cell and it would swell.