Results of the Dialysis Bag Experiment. Osmosis is the movement of water from high to low concentration across a selectively permeable membrane . When a cell is placed in a solution that has more water than the cell, the cell swells up as water crosses the cell membrane by osmosis. When a cell is placed into a solution that has less water than the cell, the cell shrinks as water leaves the cell, again by osmosis. As you might expect, drastic changes in the water concentration inside or outside of a cell can have adverse effects on the homeostasis of the cell.
Plant cells have a cellulose cell wall surrounding the cell membrane.
This places constraints on how much the cell can swell or shrink. When plant cells take on water, the cell membrane presses on the cell wall, making the cells turgid due to turgor pressure . When a plant cell loses water, the cell membrane shrivels away from the wall, plasmolysis is the term applied to a plasmolysed cell. Select a young, green leaf from the Elodea sprigs at your pods. Make a wet mount of the leaf, and observe a single cell under the 40X objective.