In osmosis, the term for a solution with lower solute concentration than the cell interior is described as?

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

Answer: (A)

In osmosis, tonicity compares solute levels outside the cell to those inside. A solution with a lower solute concentration than the cell interior is described as hypotonic. Because the outside has fewer dissolved particles, water moves into the cell to try to equalize concentrations, causing the cell to swell. In animal cells this can lead to bursting if extreme; in plant cells the cell wall prevents bursting and the cell becomes turgid. Hypertonic would pull water out and shrink the cell, isotonic would balance with no net water movement, and osmotic describes the process of water movement due to solute differences in general rather than the relative outside–inside concentration.