Andrew Dickson Background
When a plant cell is bathed in a solution of the same concentration (isotonic) as its intracellular environment, its mass and volume remain the same. This is because water enters and leaves the cells at the same rate. There is no net loss or gain of water by osmosis.
Samples of cells can be placed in a range of solutions of different concentration. The cells will gain water by osmosis when placed in solutions which are more dilute (hypotonic) than the intracellular environment. They will therefore gain mass. The cells will lose water in those solutions that are more concentrated (hypertonic) than the intracellular environment and so lose mass. The concentration of the intracellular environment of the cell can be determined by placing a sample of cells in solutions of different concentrations and determining at which concentration the cells neither gain nor lose mass. This external solution will have the same concentration (be isotonic with) as the intracellular environment of the cells.
The aim of this practical is to determine the isotonic concentration of sucrose in potato cells.
If the concentration of the sucrose solution in which the potato cylinder is bathed in changes, then there will also be a change in the mass of the potato cylinder.
Independent: Sucrose concentration
Dependant: Percentage change in mass
Other variables in the experiment are the potato which is to be controlled by having identical shaped cylinders of each. If the potato cylinders in different test tubes change in mass corresponding to the sucrose solution they are bathed in then the hypothesis will be supported. Materials
• Sucrose solution
• 5 boiling tubes
• Razor blade
• Apple corer
• Paper towel
• Petri dish
1. Label 5 boiling tubes with the concentration of sucrose solutions provided
2. Place 15cm3 of