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Investigation into the effects of osmosis on Potato cells

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Introduction

Investigation into the effects of osmosis on Potato cells PLANNING AIM The aim of this investigation is to find out the concentration of cell sap in potato tissue. Variables * Controlled-Starting length will be as close to 3.00cm possible, starting volume, which is 20ml also the same time the potato cells are kept in solution and same conditions for each cylinder. * Dependant-Length of potato cylinder (before and after osmosis has occurred). * Independent-Concentrations of solutions which are: (m) 0,0.1,0.2,0.3,0.4,0.5 Solutions Vol. Of glucose * 0.5 = M (0.5 = starting glucose concentration) Total volume 1) 0 * 0.5 = 0 M 20 2) 4 *0.5 =0.1M 20 3) 8 *0.5 =0.2M 20 4) 12 *0.5 =0.3M 20 5) 16 *0.5 =0.4M 6) 20 *0.5 =0.5M 20 20 Prediction I predict that this experiment will have different results throughout all the concentrations. Osmosis depends on two concentrations; outside (glucose solution) and inside (cell sap). I feel that my experiment will prove that osmosis has occurred meaning the water has moved form a high concentration to a low concentration. But. If the cell was already turgid when we measured it, the movement of water from a higher concentration to a lower concentration means we will find the potato cell will shrink as the solution has moved out. ...read more.

Middle

Other instruments which were the measuring cylinders - 10 ml & 25ml that are accurate to *-0.1ml & *-0.5ml respectively. This helped when I had to measure out glucose solution and distilled water. This all helped to get accurate results & a successful experiment. Strategy for results For my results for the experiment, I will make a table with concentrations down the left side and lengths of potato cells along the top. Then the percentage change in length down the right side. The title will be - -Investigation into the effects of osmosis on potato cells: Results. The graph that I will plot my results will have Concentration of glucose (M) on the X-axis and % change in length on the Y-axis. On this I will draw a best-fit line. Above the X-axis, the results are Hypotonic and below the X-axis the results are Hypertonic. But if the results are on the X-axis line, the result is isotonic meaning the concentration inside equals' concentration outside. Table and graph overleaf To find the percentage change in length, I had to use the following formula: final length - original length original length * 100 (1) 0M; 3.12 - 2.96 2.96 * 100 = 5.405% (2) 0.1M; 3.14 - 2.98 2.98 * 100 = 5.369% (3) ...read more.

Conclusion

This might be anomalous because maybe the volumes measured inaccurately or the vernier callipers were read slightly wrong. This means if there was a mistake it was because of human error. How suitable was my procedure? I feel my procedure was well suited to this investigation, because 0.25M (isotonic) fell in between 0.2M and 0.3M, meaning a perfect experiment. Also the apparatus was good enough for a successful experiment. Any changes to improve? I fell that there are many changes I could do to improve my experiment to get more accurate results. And they are: 1. Be more accurate when cutting the cylinders, try to be as close to 3.00cm as possible. If we had two different starting lengths e.g. 3.02cm and 3.12cm it would not be fair because 3.03cm chip has a greater SA: VOL giving it an advantage in terms of osmosis. 2. A third potato cylinder could be cut and put into the specimen bottle to increase accuracy in getting results. 3. A burrette could be used. These are accurate to 0.1ml, which would help when we are measuring out our solutions. 4. Also Digital Vernier callipers would be useful as we could just read off the measurement and possibly eliminate human error when measuring. Does the evidence support a firm conclusion? Yes, because 0.25M (isotonic result) corresponds with book value so this is encouraging. Five of my plotted values follow the pattern and only one is anomalous. ...read more.

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This account shows attention to detail and good use of scientific language. There are a few minor errors.

Marked by teacher Adam Roberts 01/05/2013

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