Osmosis in cells
Osmosis in living plant cells: water crosses the semi-permeable cell membrane, and the cell contents pull away from the wall in plasmolysis.
The science behind this experiment
Osmosis is the movement of a solvent through a semi-permeable membrane. In all living cells, membranes are dividers: they separate different parts of the cell from each other and impede movement of substances between compartments.
In pure water cells maintain their physiological turgor. The cell starting water potential is in equilibrium with the water potential.
Cells tend to lose water by increasing the concentration of the solution with a solute (Saccharose). The increased sucrose concentration lowers the solution water potential, draws out water from cells, and thereby reduces the cell’s turgor pressure.
The direction and rate of water flow across the membrane are determined not only by the concentration gradient of water or by the pressure gradient, but by the sum of these two driving forces.
Equipment used
- Beaker 500 ml — HEA-003
- Dropping pipette with teats — PLA-003+PLA-019
- Tweezers — PLA-025
- Scalpel — PLA-026
- Microscope slides — BIO-001
- Cover glass — BIO-002
- Microscope — BIO-009
- Tin foil
- Onion
- Small alga (Nitella)
Chemicals and reagents
- Sucrose solution
- Distilled water
Questions for students
- Report your observations and try to recognise the cells in the different conditions.
What to expect
Observing the sample with the sucrose solution the cell membrane and the cell wall cell are separated. Of course also this process is osmotic that is due to a gradient of concentration between the cell and the outer solution.
Run this experiment in your classroom
This experiment is part of ATP Volta — a self-contained mobile science lab that turns an ordinary classroom into a working STEM laboratory, with over 200 experiments in physics, chemistry, biology, robotics and engineering. Gali, the AI tutor built into ATP Connect, guides students through each step and answers their questions at the bench.
See the ATP Volta mobile science labTalk to our team