When the external solution has a higher solute concentration than the cell interior, the solution is called

• A. Hypertonic
• B. Isotonic
• C. Hypotonic
• D. Osmotic Pressure

Answer: (A)

This is about tonicity and osmosis. If the external solution has more solute than the cell interior, the outside is hypertonic. Water moves out of the cell across the membrane to try to balance solute levels, so the cell loses water and shrinks. In contrast, an isotonic solution has equal solute concentrations, so there’s no net water movement, and a hypotonic solution has less solute outside, causing water to flow in and the cell to swell. Osmotic pressure is the force driving that water movement, not a type of solution. So the described situation is hypertonic.