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Investigating the breakdown of hydrogen peroxide by the enzyme catalyse in potatoes.

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Biology Investigation By Sahlia Khan Investigating the breakdown of hydrogen peroxide by the enzyme catalyse in potatoes Wycombe High School 1/1/2010 Investigating the breakdown of hydrogen peroxide by the enzyme catalyse in potatoes Introduction This is an experiment to examine how the concentration of the substrate hydrogen peroxide affects the rate of reaction of the enzyme catalase. Prediction I hypothesise that the experiment will give results to show that as the substrate concentration increases, the rate of reaction will go up at a directly proportional rate until the solution becomes saturated with the substrate hydrogen peroxide and when molecules of the substrate are in short supply, the increase in rate of reaction is limited and will have little effect. Background Information Enzymes such as Catalase are protein molecules which are found in living cells. They are used to speed up specific reactions in the cells. They are all very exact as each enzyme just performs one particular reaction. The catalase enzyme is also found in food such as potato and liver. It is used for removing Hydrogen Peroxide from the cells. Hydrogen peroxide is a liquid which is slightly more viscous than water and appears a colourless substance in a dilute solution. It is a combination of hydrogen and oxygen, with a chemical symbol of H2O2. It has strong oxidizing properties and in high concentrations, it can be unstable and even poisonous however in a lower concentration it can work well as a disinfectant and antiseptic and is commonly found in many homes. Hydrogen peroxide is naturally produced in organisms as a by-product of oxidative metabolism. Catalase speeds up the decomposition of Hydrogen Peroxide into water and oxygen as shown in the equations below. The decomposition increases at a rapid pace due to the shape of its active site which matches the shape of the Hydrogen Peroxide molecule. A reaction like this, where a molecule is broken down into smaller pieces, is known as an anabolic reaction. ...read more.


Method The first thing to do is take safety precautions which means wearing safety spectacles to ensure protection of eyes as hydrogen peroxide is a irrtant. Then begin to collect equipment and put everything in place. A potato was collected and sliced using a potato cutter for finely cut cuboid chips. Then wrap these in cling film to stop the potatoes from oxidising. With the aid of a ruler and scalpel, long chips of potato were cut in 1cm2 cube pieces. Then get a large plastic tub and fill it with water so that it is approximately half full. After get a 50ml measuring cylinder and fill it right to the brim with water from the tap. Then cover the top of the measuring cylinder, ensuring nothing escapes and carefully tip the measuring cylinder upside down and place it in the water filled tub. Attach a clamp to the cylinder to hold it still above the base of the tub but below the surface of the water. Slot the rubber tube up the measuring cylinder, which is has been made easier due to placing the measuring above the base of the tub giving a good gap and making it easier to stick the tube along. Also the bung at the other end of the tube needs to be kept out and ready for the next stages. Get a clean test tube and using a syringe pour 10 ml of 10% concentration hydrogen peroxide in to it. Then drop the enzyme into the substrate. As soon as that happens bung the top of the test tube, whilst a partner starts the stop clock at the same time. As gas starts to escape measure the effervescence every 15 seconds using the stop clock. After recording down the results, repeat the process twice, making sure that the equipment is all reset properly. Follow this process for all concentrations of the enzyme. ...read more.


This could have been done by keeping in a cooling fridge rather than wrap the enzyme potato in cling film which was not as effective as we would have like. Despite this, overall the results show the same pattern, a correlation between the concentration of hydrogen peroxide and the amount of oxygen produced and the speed of the reaction. And also the ranges of my data were all in close quantity which does show that the data is fair and that the scale of my graphs just makes the range bars overlap. I also tried to make my lines of best fit go through most of the points that I plotted to make my data seem dependable. To improve the data, ICT could have been used to measure the experiment and draw up more accurate graphs and I believe that my lines of best fit were not as accurate was they could have been due to a bumpy ruler. Evaluation of Conclusion The conclusion I have made detailing the amount of concentration of enzyme is accurate as my collected data fully supports it and shows that as the concentration of the enzyme (potato) increases the faster the breakdown of the substrate (hydrogen peroxide). The graphs I have created fully back up my hypothesis as they show a positive correlation. If this experiment was to be completed again I would make certain that the result collected would be as accurate as possible and cut out the risks of human error. I would also try to use better equipment for precision and use more technological advanced apparatus however I am aware that this requires a lot of money and therefore would concentrate on making our equipment was set up as best as it could be in order to ensure more accurate results. I would also like to spread this over a larger amount of time so that more results can be recorded and consequently the results would be more reliable and would help us make better conclusion. ?? ?? ?? ?? Sahlia Khan Candidate No. 6412 Wycombe High School Centre No. 52433 ...read more.

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Here's what a teacher thought of this essay

4 star(s)

**** A very good GCSE level experiment report, containing a clear method based on a relevant trial experiment. Results tables, conclusions and data interpretations are clear but the evaluation needed more detailed suggestions for improvements to the method.
A testable hypothesis has been formulated and stated concisely. Biological knowledge was used to explain the prediction. The key variables were described but not all were controlled in the course of the experiment. The writer needs to double check the spelling of technical terms- catalyze is not the same as catalase.
To improve:
All written methods should usually now contain a risk assessment table to show the risks, hazards and emergency procedures to be used in an experiment. The background research would benefit from more in depth research using selected secondary resources.
Carrying out:
The results were recorded clearly and accurately in tables but some headings needed additional information added. The range and number of observations was good.
Analysis and Evaluation:
The graph was not included in this report but the student obviously used numerical evidence to to process the data for the conclusion. The student drew a conclusion consistent with the evidence and explained it using scientific knowledge and understanding. The possible explanation for anomalous results was given and how the results support the original prediction.
The evaluation could be improved by giving concrete suggestions for improvements to the method. The suggestion 'use ICT' does not explain how this improves the reliability of the evidence. The proposed equipment or modification should be given in detail.

Marked by teacher Stevie Fleming 29/05/2013

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