Osmosis and Volume

We look at the effects of osmosis on the volume of potato and the appearance of red onion cells. Two cylinders of potato are measured and weighed before one is placed in salt water and the other in fresh water. We can see how osmosis affects the different samples. We also use a microscope to look at how onion cells change when they are exposed to salt water or fresh water. Biology - Cells And DNA - Learning Points. Diffusion is the movement of liquid or gas particles from high to low concentrations, down a concentration or diffusion gradient. Osmosis is the movement of water across a semi-permeable membrane from a weak solution to a more concentrated solution. A semi-permeable membrane allows certain types of molecules to pass through it, but not others. Something is turgid when it is firm and swollen with water. Plasmolysis is the process in plants where the cell membrane pulls or shrinks away from the cell wall due to loss of water through osmosis. The cells are said to be plasmolysed. A Twig Experiment Film. Let students experience real experiments in lab conditions anywhere, from setup, method all the way through to analysis and real-world application.