movement of water into the hypertonic solution. If a cell is hypotonic relative to its environment, it has a lower concentration of solutes and higher water concentration, thus water will diffuse out of the cell – down the concentration gradient of the water. In the case of a plant cell with a cell wall, this hypotonic cell would lose water to the environment resulting in the plasma membrane collapsing inward, concentrating the organelles, and pulling away from the cell wall. This process is called plasmolysis. Experiment 1. Osmosis in Potatoes: The osmolarity of a cell is the total concentration of solutes (in the solvent water) that affects osmosis. Plant cells, such as those in potato tubers, contain many osmotically active solutes, such as proteins and polysaccharides, which contribute to the total osmolarity of those cells. In this experiment, potato pieces will be incubated in seven different concentrations of a solute, ranging from none (0 M) to 0.6 M. Some of the solutions may be hypotonic, others hypertonic, and maybe even isotonic to the potato cells. During the brief incubation period, water will be the primary molecule that will be transported across the plasma membranes into or out of the cells. By measuring the mass of the potato pieces before and after incubation, the gain or loss in water due to osmosis can be determined. From this information you should also be able to calculate the osmolarity of potato tubers. 1. Label seven beakers on your tray as: DI water, 0.1 M, 0.2 M, 0.3 M, 0.4 M, 0.5 M, and 0.6 M. Then pour the DI water (carboy by the sink) or appropriate sucrose solution (from the demo area) into each of the beakers. Pour in an amount of solution that you think will be enough to cover the potato strips. Be conservative - if you find you need more solution once you add the potato, you can add more at that point. 2. Obtain 7 already cut potato strips from the beaker in the demo area and place in a weigh boat. Using a razor blade, trim the potato strips to a length of 5 cm and trim off any potato peel, if present. 3. One at a time, gently blot a potato strip with a paper towel and place in a clean, dry weigh boat on the tared (or zeroed) balance and record the mass in Table 1 "Initial Mass (a) " Place the first potato strip