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The aim of this experiment is to demonstrate that the substrate Hydrogen Peroxide will break down to oxygen and water, in the presence of the enzyme catalase.

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BIOLOGY AS LEVEL KATHERINE WYATT ANALYSIS AND EVALUATION OF COURSEWORK EXPERIMENT 5 DECEMBER 2002 COURSEWORK EXPERIMENT Further to the 'Coursework Plan' which was submitted to my tutor on 5 December, outlining a plan for conducting an experiment 'to establish that varying the surface area of catalase exposed to the substrate Hydrogen Peroxide will affect the rate of the reaction', all students were given a 'Student Worksheet', which detailed the prescribed apparatus and methodology for conducting the experiment. The following information will outline the evaluation and analysis of this experiment, under the following headings: * Introduction; * Prediction; * Variables; * Preliminary Work; * Method; * Results; * Conclusion; * Interpretation; * Evaluation. INTRODUCTION The aim of this experiment is to demonstrate that the substrate Hydrogen Peroxide will break down to oxygen and water, in the presence of the enzyme catalase. The catalase will be obtained from potatoes. This experiment also aims to investigate and demonstrate that an increase in the surface area of potato (catalase), placed in equal volumes of Hydrogen Peroxide, will increase the activity of catalase and hence increase the level of oxygen production. This will demonstrate an increased rate of catalase reaction. Specifically, with regard to this experiment, Catalase is a biological enzyme, which helps to speed up the reaction between catalase (found in potato) and the breakdown of Hydrogen Peroxide. Most intracellular enzymes work only on one particular substrate. Catalase, for example, acts only on Hydrogen Peroxide, and is ineffective on any other natural substrate. The active site is contained within the enzyme (Lock), and once the substrate (Key) is locked into the active site, the reaction takes place. The products (oxygen and water) will then be released, and the enzyme will move on to another substrate (Hydrogen Peroxide). PREDICTION The experiment, therefore, aims to demonstrate firstly an enzyme reaction between catalase (found in potato) and Hydrogen Peroxide; and secondly, the speed of the reaction when the surface area of the potato is increased. ...read more.


8. MEAUREMENT OF TIMINGS: Every 30 seconds, I then measured the volume of oxygen that had been released in the experiment, by taking the manometer reading and recording this in the table, for 5 minutes. 9. DISCARD: After each experiment, all contents of the boiling tube were discarded in a central beaker, for use by all students. 10. REPEAT OF EXPERIMENT: In order to enable an average result to be taken, the same experiment was conducted for the same sized potato sample, and accordant results were then inserted into a secondary table. 11. FURTHER SAMPLE SIZES OF POTATO: I then took a secondary sample of potato, utilising the cork borer and cleaned with the distilled water. Utilising the scalpel and tile, I then completed the experiment, as outlined in steps 5 - 10, for pieces of potato as follows: 4 cm x 1 cm; 3 cm and 2 cm; 3 cm and 2 x 1 cm; 5 x 1 cm. 12. RECORDING OF OXYGEN PRODUCTION: When the previous steps has been achieved, the timings and total volume of oxygen collected (cm3), should be noted in a result table, as outlined in 'Results'. If bubbles are still being produced, then oxygen is also still being produced. The clamp was then opened to allow the gas to be released. The manometer fluid was then return to its original level, thus ensuring accurate readings. 13. CLEARING UP: Following the completion of all the experiments, as outlined above, I then disposed of all of the potato and fluids utilised in the experiment, and cleared all the apparatus away and cleaned up the experiment surfaces. RESULTS This experiment provided the volume and rate (in cm3) of oxygen produced at varying times, by identifying the levels of oxygen gas which are given off in the space of 5 minutes for the various concentrations of potato samples, as outlined in the 'Table of Results' (Below). ...read more.


Evaluation Issue Number 7: * The Hydrogen peroxide did not always cover all of the potato, thus reducing the effect of increased surface area Suggested Improvement: In future, I should increase the quantity of Hydrogen Peroxide, ensuring that the same quantity is used for each experiment, however. Evaluation Issue Number 8: * A change in pH may have had an impact upon the results. Suggested Improvement: In order not to disrupt the results, pH 7 buffer should be selected and inserted into the boiling tube, to match the natural pH of the potato tissue and therefore match the enzyme, to ensure that it is able to work effectively. Evaluation Issue Number 9: * I felt clumsy and unconfident in this experiment, due to lack of expertise and previous practice with the experiment equipment. Suggested Improvement: In future, I would like to conduct more experiments, and certainly have a pilot experiment, to ensure that I am confident in the use of all of the equipment. Accuracy of Results Although I have commented (above) on suggested improvement to the experiment, on a more positive note, to conclude, I can confirm that I restricted the variables to only one - being that of the increased surface area of the potato (catalase). This ensured that the experiment was completed as fairly as possible, ensuing that all the variables except for the varying surface area of potato, remained the same for all of the experiments. I can also confirm that completing each different groupings of potato twice, and thus calculating an average for these results, should have guaranteed more reliable results. I also measured the volume of Hydrogen Peroxide very accurately with a pipette and filler, ensuring that that meniscus was accurate. In summary, the experiment did conclude that which I had detailed in the 'Prediction' of the experiment, however, further improvements as outlined (above) would ensure that a repeat of this experiment, would attain more accurate and thus conclusive results. ...read more.

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