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Influence of pH on the activity of potato catalase

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INFLUENCE OF PH ON THE ACTIVITY OF POTATO CATALASE Aim: Investigation how pH affects the activity of potato tissue catalase, during the decomposition of hydrogen peroxide to produce water and oxygen Hypothesis: The activity of catalase in potato tuber depends heavily on the pH. One of the pH provides optimum condition for the enzyme, probably the pH 7. Apparatus: * Potato * Razor blade * Cork borer * Potato tuber * Boiling tube * Stand, bosses and clamps * Manometer tube * Beaker * Syringe * Clip * Clock * Wax pencil * Hydrogen peroxide * 0.2 mol dm-3 Citric acid phosphate buffer * 0.1 mol dm-3 Citric acid buffer * Pipettes Introduction: Catalase is an enzyme found in all living tissues that speeds up the breakdown of hydrogen peroxide, its substrate. Hydrogen peroxide (H2O2) is a poisonous byproduct of metabolism that can damage cells if it is not removed. The reaction catalase promotes is as follows: 2H2O2--------catalase--------------> 2H2O + O2 To keep the catalitical activity still, enzymes need a suitable pH. For most of enzymes optimal pH is 5,5-7,4. PH dependence on enzyme's activity is one of the most essential factors regulating the speed of the reaction. ...read more.


Table 4: The standard deviation calculated for each pH Time Trial [s] �0.5 s pH 3.0 4.0 5.0 6.0 7.0 8.0 First 195.0 146.0 148.0 128.0 53.0 52.0 Second 197.0 163.0 151.0 158.0 55.0 55.0 Third 198.0 172.0 162.0 162.0 59.0 64.0 Fourth 212.0 180.0 167.0 169.0 70.0 71.0 Fifth 221.0 191.0 172.0 187.0 80.0 82.0 Sixth 237.0 204.0 188.0 185.0 83.0 98.0 STANDARD DEVIATION: 16.0 18.7 13.4 19.7 11.8 15.9 Rounded to 1 decimal place Table 5: Mean, standard deviation, range. pH Mean [s] SD range % 3.0 216.0 16.0 200.0-232.0 <68% 4.0 175.0 18.7 156.3-193.7 <68% 5.0 168.0 13.4 154.6-181.4 <68% 6.0 156.5 19.7 136.8-176.2 <68% 7.0 68.0 11.8 56.2-79.8 <68% 8.0 75.0 15.9 59.1-90.9 <68% None of the data fits in 68% of the results, so I decided to exclude 2 of 6 trials to get a more reliable results. Table 6: The time it takes for the fluid to rise through the distance of 5 cm in diversified pH Time Trial [s] �0.5s pH 3.0 4.0 5.0 6.0 7.0 8.0 First 195.0 163.0 151.0 158.0 55.0 55.0 Second 198.0 172.0 162.0 162.0 59.0 64.0 Third 212.0 180.0 167.0 169.0 70.0 71.0 Fourth 221.0 191.0 172.0 187.0 80.0 82.0 Rounded to 1 decimal place Table ...read more.


* Potatoes of different kind * Difference In thickness and size of potato * Not exact amounts of substance * Not mixed solution * Not exact pH * Different amount of enzymes in potato * Not exactly dried potato discs * Not exactly cleaned boiling tubes * Lopsided apparatus * Uneven apparatus * Unclean syringe * Leaky spring clip * Imprecise clock * Human reaction in measuring time * Lack of organisation To improve the result, I could: * Follow the plan step-by-step * Make more measurements to reduce the uncertainty * Pick a potato of the same kind so the amount of enzyme is the same in each potato disc * Be more precise when cutting a potato to have the same size of discs * Check and use the equipment which isn't faulty * Use the clock with measures time with more decimal places to decrease the uncertainty * Make sure I do the experiment correctly by consulting the teacher or biochemical books If the improvements I recommended were made, the results of the experiment would be more precise and accurate. Some of the errors were unavoidable, but some of them like human reaction or lack of organisation could be handled better and therefore avoided. ?? ?? ?? ?? Gracja Kowalska kl. II ib 2008-11-18 ...read more.

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