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Osmosis in potato cells.

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Introduction

Osmosis in potato cells Aim- To investigate the effect of different concentrations of sugar solutions on potato cells. Planning a simple procedure- In this experiment I will try to find out how different concentrations of sugar solutions will affect osmosis in potato cells. Using a cork borer, I will cut out several pieces of a potato of uniform cross-section. I will then cut this uniform cross-section of the potato into pieces of equal lengths, using a scalpel. This is important, as the surface area is one of the factors that affect osmosis. I will then place them in different, pre-prepared sugar solutions of concentrations 0 - 100%. Preliminary Work- Prior to this experiment: * We did an experiment using 0%, 10% and 50% concentrations of sugar solutions. We placed two pieces of potato in each petri dish. Therefore, ending up with two results for each concentration. From this experiment, I discovered that in distilled water the potato increased in length and in, between 10% and 50% concentrations, the potato pieces decreased in length. Therefore I decided to focus my investigation on solutions of 10 - 50 % concentrations. * I did some research to find out what factors affect osmosis. These were as follows: 1) Surface area of the potato sample. ...read more.

Middle

This is because if one of the samples was longer it will have a larger surface area and osmosis will occur quicker. 2. Temperature- the temperature may affect the reliability of the experiment as large variations of temperatures will affect the cell walls of the potato pieces because the cells would dilate differently at different temperatures, thus affecting the surface area. The movement of water molecules will also vary at different temperatures. To prevent this from happening, all the beakers were kept in the same place, at room temperature. Evaporation of water will also be controlled by covering the beakers with petri dishes, thus maintaining the concentration level of the solution. 3. Use the same potato- because there could be a variation in the texture and sugar content between different potatoes. 4. Contamination- the beaker used to measure out the sugar solution should be washed and dried each time, as different concentrations of sugar solution could get mixed up. There were five different concentrations of sugar solutions: 0%, 8.5%, 25.5%, 34% and 51%. The results were also taken four times and an average was then taken to provide more accurate results. Average- to make the experiment as accurate as possible, an average will be taken from the four results from each concentration of sugar solution. ...read more.

Conclusion

At this point there is no net flow in either direction of the cell membrane. This is the point at which sugar concentration in the potato is the same as the % sugar concentration of the solution. The reading on the x-axis gives the % sugar level in the potato. From graph 1, graph showing % solute concentration against % change in length, the % sugar in my potato is approximately 6% and from graph 2, graph showing % solute concentration against % change in mass, the % sugar in my potato is approximately 7% I have drawn a line of best fit for readings of 0%, 25.5% and 34% because these points are almost on a straight line. The gradient after the 34% solute concentrations is much slower representing small % changes at higher solute concentrates. Section E (Evaluation) Having taken steps to make this a fair test I think my results were relatively accurate. I have obtained very close figures for sugar content in the potato from both the graphs. The following should be considered to improve this experiment: 1. Human error- errors made in reading the correct lengths and mass and obtaining correct % solute concentrations etc. 2. Care should be taken not to allow the potato pieces to dry out excessively or gain moisture from the surrounding. 3. Use a digital balance accurate to 0.01g December 2002 December 2002 December 2002 ...read more.

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