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  • Level: GCSE
  • Subject: Science
  • Document length: 3175 words

An investigation into the effect temperature has on the activity of the enzyme catalase in the breakdown of hydrogen peroxide into water and molecular oxygen

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Introduction

An investigation into the effect temperature has on the activity of the enzyme catalase in the breakdown of hydrogen peroxide into water and molecular oxygen .....In an enzyme-catalyzed reaction, the substance to be acted upon binds reversibly to the active site of the enzyme. One result of this temporary union is a reduction in the energy required to activate the reaction of the substrate molecule so that the products of the reaction are formed. 2H2O2 =2H2O + O2 Catalase is an enzyme present in the cells of plants, animals and aerobic (oxygen requiring) bacteria. The enzyme catalase decomposes hydrogen peroxide (H2O2) into water (H2O) and oxygen (O) gas. Although enzymes are sensitive molecule, enzymes are very specific; they are made up of globular protein which had polypeptide chains. Enzymes work in a reaction by fixing themselves to substrates, these reactions can be described as catabolic or anabolic. The theory behind enzyme reactions is often described as 'lock and key'. This theory relies heavily upon the idea that the protein which the enzyme is made of keeps its specific shape. Catalase has a narrow range of conditions under which it can function properly. These conditions are called variables. These variables affect the enzyme kinetics. The independent variables in this reaction are substrate concentration, temperature, PH and the enzyme concentration. Independent variable: temperature However in my experiment I am going to investigate the affect temperature has on the rate in which the enzyme catalase reacts with hydrogen peroxide to produce hydrogen and oxygen. In general, chemical reactions speed up as the temperature is raised. When the temperature increases, more of the reacting molecules have the kinetic energy required to undergo the reaction. Enzyme catalyzed reactions also tend to go faster with increasing temperature until a temperature optimum is reached. Above this value the conformation of the enzyme molecule is disrupted. Changing the conformation of the enzyme results in less efficient binding of the substrate. ...read more.

Middle

Therefore my results will be accurate, the only gas that I will account for is the oxygen produced, during the reaction between hydrogen peroxide and catalase. List of equipment: * 3 Conical flasks * 3 tubes * 1 gas syringe * 20ml measuring cylinder * 1 scalpel * 1 Ruler * 1 thermometer * 1 water bath * 1 clamp and stand * 1 stop watch * Hydrogen peroxide (20% concentration) * PH7 buffer * Potato * Potato chip cutter Method * Set up water bath at 5 degrees centigrade, and leave for a few minutes so the device can reach the correct temperature. Then test the water in the bath with a thermometer, ensure it is at the correct temperature. * Set up the rest of the equipment; attach clamp to stand and secure the syringe to the clamp with the tubing attached. Above the water bath in preparation. * Measure 20ml of hydrogen peroxide (20% concentration) in a 20ml measuring cylinder. Then pour this substance into a clean conical flask ensuring not to spill any or leave any in the cylinder. * Measure 10ml of PH7 buffer in a 20ml measuring cylinder, add this substance to the hydrogen peroxide in the conical flask. (use a universal indicator to check the PH is neutral) * Dip the end of the universal indicator paper into the solution. And compare the colour against a colour pH chart, to ensure the solution is at the correct pH. * Leave the substance for a minute, so that it can acclimatise to the temperature and ensure there is no air being produced from the hydrogen peroxide decomposing on its own. * Place the conical flask in the water bath * Place a potato in the chip cutter, to get long 1cm cubed width chips. Then ensure you use the pieces which do not have skin on them. Then line the potato chip up to the ruler's edge, and then cut directly downwards (so that it is not at an angle) ...read more.

Conclusion

The temperatures which I chose were ideal for this broad experiment, to gage the general reaction of the enzyme catalase to see the effect temperature had on its rate of reaction. However it would be very useful to decipher the specific rates of reaction around the optimum temperature. The optimum temperature is a vital stage in the enzymes, therefore in the next experiment I should concentrate around the area of 25 to 30 degrees centigrade. This would show the rate at which the hydrogen bonds in the protein of the enzyme were broken and the active site was distorted. Also the interval between the temperatures that I tested at was fairly large, so the rate of reaction could have varied between these temperatures. This means that the shape of my graphs could be altered by an anomalous result at the temperature at which I tested. If I had tested at intervals of 1oC, an incorrect result would not affect the shape of my graph a great deal. However, it was impossible for me to conduct the experiment at temperatures that increase by only 1oC because I would not have had time and because I would not have been able to accurately maintain the temperature. It is also possible that the catalase did not have time to acclimatise to the change in temperature. This would have resulted in the reaction occurring more slowly at the beginning of the experiment than it would have if the catalase enzyme started at the correct temperature. This error could have been avoided by allowing the solution and the enzyme time to acclimatise to the temperature. Finally the last misjudgement I have made in my experiment was the subjective process of determining the temperature at which to end the experiment. I stopped at 60 degrees centigrade, although from my results you can see that there is still a reaction occurring. If I repeat this experiment I should continue with higher temperature until the enzyme fully stops reacting. ...read more.

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