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Potatoes and Osmosis.

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Introduction

Potatoes and Osmosis INTRODUCTION: Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. Diffusion results because of the random movement of particles. The diffusion of water into and out of a selectively permeable membrane is called osmosis. Because of the selectively permeable membrane, nothing but water and other very small particles can be diffused through osmosis. The cell membrane is similar to the membrane mentioned above, so the cell would lose water because of osmosis if it were placed in an environment in which water concentration is greater than that of the cell. A solution is isotonic if the concentration of dissolved substances is the same as the concentration inside the cell. Osmosis does not occur in an isotonic solution. A hypotonic solution is a solution in which the concentration of dissolved substances is lower than the concentration inside the cell. If a cell were put in a hypotonic solution, osmosis will cause water to move through the cell membrane into the cell. A solution is hypertonic if its concentration of dissolved substances is greater than the concentration inside the cell. ...read more.

Middle

Potato cores were cut approximately 5 cm for each test tube, the cores are weighted and placed in the test tubes. After that, the solutions are placed in the test tube according to their labels. The solutions will be in the test tube for 1hr 18min. After 1hr 18min, the cores are taken out of the solutions and blotted dry. Their volume and weight is recorded (please refer to table 1). The percent change in weight and volume is calculated and recorded for each sample (please refer to table 2). RESULTS For the 0.0 distilled water concentration the percent change in weight was -34%, for the 0.1 sucrose concentration, it was -33%, for 0.2 it was -35%, for the 0.3 concentration it was -36%, for the 0.4 sucrose concentration, the percent change in weight was -39%, for the 0.5 concentration it was -42%, and for the 0.6 concentration it was -48% (please refer to table2). The reason for the change in weight is the process of osmosis. All of the potato cores in the experiment lost weight making them (hypertonic). When the sucrose concentration was 0.3, it should have been isotonic, so that no major exchange of particles occurred between the potato cells and the sucrose solution. ...read more.

Conclusion

I think we had an error because all of the potato cells in the experiment lost water making all of them hypertonic. Maybe we should have left the potato in the sucrose longer. I would think that when the distilled water concentration was 0.0, the cores should have gained weight because the concentration in the potato cells would have been different from the concentration outside allowing more water to come in so it will reach a dynamic equilibrium with the outside of the cell. Our results should have looked like Table 3. These results would show that when the distilled water concentration was at 0.0 the potato cell gained weight. Sucrose concentration at 0.1 and 0.2 lost the least amount of weight. From this result you can see that 0.3 would be the potato cells osmolarity, which is what I also concluded from our results. It should have been isotonic, so that no major exchange of particles occurred between the potato cells and the sucrose solution. Higher sucrose concentrations 0.4, 0.5, and 0.6 all lost the most amount of weight. From this data we can determine that the lower the sucrose concentration causes the least amount of weight loss and the higher sucrose concentration causes the most amount of weight loss (hypertonic). 1 ...read more.

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