lab report 4
Alibrahim
Exp4sp2019.pptxOsmosis
Onion Cells
Diffusion of Water across Cell Membranes: Osmosis:
Water is one molecule that can easily cross the cell membrane. The net diffusion of water through a selectively permeable membrane from the side of high water concentration to the side of a lower water concentration is termed osmosis. When a cell is placed in a solution in which the concentration of all solute particles is lower than the cell( and therefore, the concentration of water is higher), then water will move into the cell. Such a solution is called hypotonic. If the solute molecules are unable to pass through the cell membrane, a hypotonic solution will cause a cell to swell from the osmotic up-take of water. Conversely, if a cell is placed in a solution with high particle ( low water) concentration relative to the cell, that cell will loose water. The letter cell is a hypertonic solution, defined as a solution that will make a cell shrink because of the osmotic loss of water . A cell in an isotonic solution will have no net water uptake or loss. Note that each of these terms is relative to the inside of the cell.
Osmosis in plant cell
Plasmolysis is the shrinking of the cytoplasm of a plant cell in response to diffusion of water out of the cell and into hypertonic solution ( high salt concentration) surrounding the cell. During plasmolysis, the cellular membrane pulls away from the cell wall.
Procedure
In this experiment you will examine the effect of highly concentrated solutions on osmosis and cellular contents
1.Prepare a wet mount of a thin layer of onion epidermis as we did last time.
2. Examine the cell and draw it.
3. Remove the slide from the stage of the microscope.
4. Place 2-3 drops of 30% salt solution on the slide at the edge of the cover slip.
5. Examine the cell and draw what you see.
Osmosis in onion cells
