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Investigating the factors that affect the rate of reaction between the enzyme catalase and hydrogen peroxide.

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Introduction

Investigating the factors that affect the rate of reaction between the enzyme catalase and hydrogen peroxide This investigation is aiming to observe the effect temperature has on the rate of reaction between the enzyme catalase and hydrogen peroxide. This reaction will occur at a range of controlled temperatures to determine the effect various temperatures have on this enzyme-substrate reaction. Prediction Enzymes are biological catalysts, and as catalysts, enzymes will increase the rate at which chemical and metabolic reactions occur. In most metabolic reactions, without an enzyme the reaction would occur so slowly that they would virtually not happen at all. These specialised protein molecules are produced in cells, and are used to speed up virtually every metabolic reaction that occurs within a living organisms by binding a substrate to the active site of an enzyme. This causes the shape of its molecule to alter slightly, thus making it 'easier' to change the substrate into a product, as the activation energy would be lower. Enzymes are large, complex globular proteins, which like all globular proteins are coiled up into a precise three-dimensional structure, with hydrophilic R groups on the surface of the molecule ensuring the solubility of the enzyme. The enzymes specificity arises from its active site, which is a region, usually a cleft or depression, to which a particular substrate can bind. The shape of the active site permits the substrate to fit perfectly, and to be held in place by temporary bonds, which form between the substrate and some of the R groups of the enzyme's amino acids. ...read more.

Middle

3. Put thermometers in each conical flask. 4. Place both conical flasks into the water bath (which should have reached the desired temperature). 5. When both the enzyme and substrate have reached the desired temperature, note the temperature. 6. Pour the substrate into the flask containing the catalase, and rapidly place the bung in the conical flask and start the stopwatch. 7. Record the amount of gas produced every 10 seconds for 300 seconds. 8. Repeat for each temperature. 9. Repeat these steps three times for each temperature, and record in a table. 10. Calculate the average amount of gas produced for each 10 second period for each temperature. 11. Record results in a table and transcribe onto graphs showing the rate of reaction for each temperature used, and the effect of temperature on the rate of an enzyme-controlled reaction. To calculate the initial rate of reaction you will have to calculate the gradient of the tangent of the curve on the graph. Risk Assessment 1. Hydrogen peroxide is an irritant so goggles and any other available protective clothing should be worn, in the event of a spillage. 2. Catalase poses a minimal risk but enzymes can act as an irritant to some people, especially those who suffer from eczema. If you are at risk then wear protective gloves when handling the enzyme. Any spillages should be cleaned away immediately. 3. Waste. Any waste should be disposed of in the waste bucket. Do not pour down the sink, as vast quantities of hydrogen peroxide in a water system can be dangerous. ...read more.

Conclusion

This error could have also occurred when using the hydrogen peroxide. If the concentration of hydrogen peroxide became more dilute than usual then that would also produce a similar outcome. 4. A great error could also have occurred from the time delay between mixing the catalase and hydrogen peroxide and placing the stopper on the top of the conical flask and starting the stop watch. This error could account from the anomalous results experienced at "0.7�C and 30�C. Overall, I believe that my results are as accurate as it is possible to make them with the apparatus that was available. However, the validity and reliability of the results could have been improved by carrying out a greater number of replicates, as there were a couple of minor anomalies present. For example, at 25.4�C where the calculated rate of reaction was 0.178 cm3/sec, and at 20.7�C where the rate of reaction was 0.015 cm3/sec. However, excluding those two minor anomalies, I believe that I compiled and interpreted reliable and accurate evidence to support my original hypothesis. Limitations 1. The gas syringes were only accurate to 0.5 cm3. It would have been more accurate to use a burette to measure the amount of oxygen produced. However, the burette was too accurate in this case as this piece of apparatus made it impossible to record the volume, as the volume altered so rapidly. 2. The enzyme did not remain constant, because this experiment was performed over a one week period, fresh enzymes had to be prepared. But you could minimise the error by carrying out a larger number of replicates. ...read more.

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