When a cell is placed in a hypotonic solution, the solute concentration outside the cell is lower than inside the cell, and the osmotic pressure gradient forces water into the cell. Depending on the amount of water that enters, the cell may look enlarged or bloated. If the water continues to move into the cell, it can stretch the cell membrane to the point the cell bursts (lyses) and dies. This process is known as cytolysis. In contrast, if a cell is placed in a hypertonic solution, the solute concentration outside the cell is higher than inside the cell, and the osmotic gradient causes water to rush out of the cell, causing it to shrink and shrivel. In an isotonic solution, there is no net movement of water, and the cell remains the same size.
It is important to note that plant cells respond the same way as animal cells in a hypotonic solution, but the effects may not be as severe. Plants have rigid cell walls made of cellulose covering the plasma membrane, which makes it difficult for the cell to lyse, but the increased pressure can cause the cell to become turgid.
