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Isotonic Point of Potatoes

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Introduction

Isotonic Point of Potatoes - Biology Lab Report Topic: Chemicals of Life Research Question: To find the isotonic point of potato (Solanum tuberosum) by varying the concentration (M) (+/- 0.06 M) (0.10,0.15,0.20,0.25,0.30 M) and measuring the change in length of potato strips (cm) (+/- 0.01 cm). Background Information: Isotonic Point: The isotonic point is the point where the concentration of the solution is the same as the concentration of the cell. It means that there are equal amounts of 'free' water (not bound to solutes) in the solution and the potato. http://uk.answers.yahoo.com/question/index?qid=20061216095625AAOZv8h Potato: A plant tuber, Solanum tuberosum, eaten as a starchy vegetable, particularly in the Americas and Europe Variables: Independent: 1) Concentration of Glucose solution (M) (+/- 0.06 M) (0.10, 0.15, 0.20, 0.25, 0.30) Dependent: 1) The change in mass and length of the potato chips (cm) (+/- 0.01 cm) Controlled Variable: Method of control Initial length of the potatoes strips used for the experiment (cm) (+/- 0.01 cm) The potatoes will be cut to a specific initial length before using them in the experiment using an accurate measuring instrument and a scalpel Volume of the Glucose solution (cm3) Using a measuring cylinder (+/- 0.05 cm3) the same volume of water will be measured out for each solution.

Middle

(+/- 0.05 cm) 0.27 0.09 Table 7: Average Change in Mass, Average Change in Length for 0.15M Average Change in Mass (g) (+/- 0.01 g) Average Change in Length (cm) (+/- 0.05 cm) 0.20 0.16 Table 8: Average Change in Mass, Average Change in Length for 0.20M Average Change in Mass (g) (+/- 0.01 g) Average Change in Length (cm) (+/- 0.05 cm) 0.11 0.04 Table 9: Average Change in Mass, Average Change in Length for 0.25M Average Change in Mass (g) (+/- 0.01 g) Average Change in Length (cm) (+/- 0.05 cm) 0.02 0.03 Table 10: Average Change in Mass, Average Change in Length for 0.30 M Average Change in Mass (g) (+/- 0.01 g) Average Change in Length (cm) (+/- 0.05 cm) 0.08 0.14 Table 11: Shows the standard deviation values for the change in mass (g) (+/- 0.01 g) and length (cm) (+/- 0.05 cm) Concentration of sample in subject STDEV for change in mass STDEV for change in length 0.10 M solution 0.199173 0.022361 0.15 M solution 0.076354 0.089443 0.20 M solution 0.068557 0.054772 0.25 M solution 0.025884 0.054772 0.30 M solution 0.090719 0.089443 Graph 1: Shows the average change in mass as the concentration of the solution increases.

Conclusion

The range of the increments for the concentration of the glucose solution proved to be appropriate as an accurate estimation of the isotonic point of the potatoes was suggested. Whatever anomalous data received from the experimentation could be attributed to the uncertainties of the instruments used during the experiment as these could have caused inconsistencies and inaccuracies in the data received. Suggested Improvements: 1) To ensure accuracy in the lengths of the potato chips, use a more accurate cutting device which is easier to use and sharper so that the cut can be made easily and smoothly. Also, a more accurate measuring device should be used, for example, a vernier calliper. 2) To ensure accurate mass readings, a more efficient drying process should be made as the mass of extra water on the surface may have affected the readings. Using acetyl alcohol as a drying agent may be a better option. 3) Have prepared glucose solutions made by professionals to avoid inaccuracies in the specified concentration of the glucose solutions in use. 4) Use a potato chipper to cut the potatoes into an even and similar shape to avoid inconsistencies in the surface areas of the potatoes used in the same sample as it would lead to different rates of diffusion leading to inaccuracies in the experimental data. ?? ?? ?? ?? Rushikesh Birewar Class 12 Biology HL

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