however if solutions are NOT isotonic, cells are affected.
if the solution has a more negative water potential (stronger sugar concentration outside the cells than inside the cells) then water will leave the cells to try to even the water potentials. If an animal cell, the cell will shrivel up and if it is a plant cell, the cell membrane will shrivel up but the cell will keep its structure because of its cell wall.
if the solution has a more positive water potential then water will enter the cell. If too much water enters the cell, then in an animal cell the cell will burst - lysis - and in a plant cell, a series of events will happen. First the cell membrane will expand until it bursts like in the animal cell. However there is still a cell wall but this is but semi-permable so fluids freeloy move pass it. The outside solution will fill into what is left of the cell. This is called plasmolysis.
nice