The side of a cell membrane with fewer particles is described as?

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

Answer: (C)

Tonicity explains how the solute concentration compares across a membrane and predicts water flow. If one side has fewer particles, it has a lower solute concentration relative to the other side, so that side is hypotonic. Water moves toward the side with more solutes (the hypertonic side), which is why the side with fewer particles is described as hypotonic. If concentrations were equal, it would be isotonic; if that side had more particles, it would be hypertonic. Osmotic describes the movement of water itself, not the state of the side.