Solutions

Isotonic, hypotonic and hypertonic

Osmosis

Cells in solutions experience osmosis. Osmosis is the diffusion of water across a selectively permeable membrane.

Isotonic, hypotonic and hypertonic solutions have different effects on cells.

Isotonic solution

In an Isotonic solution the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside the cell.

Cells in isotonic solutions do experience osmosis, but water diffuses into and out of the cells at the same rate. Cells retain their normal shape.

Hypotonic solution

In a hypotonic solution the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell.

Cells in hypotonic solutions experience osmosis. Water moves through the plasma membrane into the cell and the cell swells. Animal cells may continue to swell until they burst and plant cells swell beyond their normal size as pressure increases, but they don't burst.

Hypertonic solution

In a hypertonic solution the concentration of dissolved substances is higher outside the cell than inside the cell.

Cells in hypertonic solutions experience osmosis. The water flows out of the cell and the cells get smaller. Animal cells shrivel up and plant cells lose pressure as the plasma membrane shrinks away from the cell wall.

Henrieta Kopnicka