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An Investigation of the Effect of Copper Sulphate on Catalase Activity.

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Introduction

Matthew Scott 04/11/01 An Investigation of the Effect of Copper Sulphate on Catalase Activity Introduction Catalase is an enzyme which catalyses the reaction between hydrogen peroxide (H2O2) is broken down into oxygen (O2) and water (H2O). catalase 2H2O2 2H2O + O2 The heavy metal ions Cu+2 in copper sulphate inhibit this reaction. Copper sulphate is an irreversible non-competitive inhibitor. Scientific Knowledge Five main factors effect enzyme controlled reactions. They are: temperature; pH; substrate concentration; enzyme concentration; and, whether or not inhibitors are present. Therefore to investigate the effect of copper sulphate on catalase activity the temperature, pH, substrate concentration and enzyme concentration must be kept constant throughout the experiment. The factor to be investigated is the addition of inhibitors as it is the only factor to be varied. Enzymes are protein molecules, which act as biological catalysts. They contain an active site to which a molecule or molecules can bind. This molecule is known as the substrate of the enzyme. While bound to the active site (by temporary bonds formed between some R groups of the enzyme's amino acids, and the substrate), bonds are broken or formed in the substrate molecule and a product or products leave the active site. This is shown in Figure 1. Figure 1. A simplified diagram to show the function of an enzyme. Each enzyme is specific to one substrate as their active sites are shaped to enable one shape of the molecule to fit. The addition of certain molecules to this process can prevent it from taking place. This reduces the rate of an enzyme controlled reaction. Such molecules are known as inhibitors. There are two types of inhibitors: competitive; and, non-competitive. Competitive inhibitors are similar in structure to the substrate so compete with the substrate for the active site. They can fit into the active site and form an enzyme inhibitor complex so the substrate is unable to enter the active site. ...read more.

Middle

* Those handling the substance should wear rubber gloves and wash their hands thoroughly afterwards to prevent poisoning themselves or others. * Safety spectacles to prevent any risk of an eye injury. * Work with the liquids whilst standing up. Never sit down. Standing up enables one to move quickly if there is a spillage. * When the experiment has been completed always thoroughly wash the equipment used. Wipe down benches so that they are clean surfaces. Table 1. A table to show the values (in cm3) read from the burette Time (seconds) Concentration Of Copper Sulphate (mols) Start Volume (cm3) 20 40 60 80 100 120 140 160 180 0.0 47.5 46.8 45.2 43.7 42.5 41.2 40.1 39.0 38.1 37.1 0.1 45.4 44.9 44.4 44.0 43.6 43.2 42.7 42.3 41.9 41.5 0.2 40.1 39.4 38.9 37.5 37.2 36.8 36.4 36.0 35.6 35.2 0.3 49.2 48.8 48.5 48.1 47.8 47.5 47.2 47.0 46.7 46.5 0.4 45.8 45.3 44.9 43.5 43.1 42.8 42.4 42.1 41.9 41.7 0.5 46.1 45.7 45.4 45.1 44.9 44.7 44.4 44.0 43.8 43.5 Table 2. A table to show the amount of oxygen produced when a further 20ml of hydrogen peroxide was added to the inactive reaction Concentration Of Copper Sulphate (mols) Number Of Repeat Amount Of Oxygen Produced (cm3) 0.5 1 0 0.5 2 0 0.5 3 0 Table 3. A table to show the values (in cm3) read from the burette collected from a separate investigation Time (seconds) Concentration Of Copper Sulphate (mols) Number Of Repeat Start Volume (cm3) 10 20 30 40 50 60 0.0 1 41.0 35.4 29.9 24.4 20.5 17.9 15.4 2 48.1 46.1 39.5 32.4 27.5 23.6 20.1 3 48.1 45.5 40.0 36.3 32.5 29.9 26.8 0.2 1 42.6 42.2 42.0 41.8 41.6 41.5 41.4 2 48.2 47.6 47.4 47.2 47.0 46.9 46.8 3 37.5 37.1 36.9 36.7 36.5 36.4 36.3 0.4 1 47.1 46.8 46.4 46.3 46.2 46.1 46.0 2 49.3 49.0 47.7 47.5 47.4 47.3 47.2 3 45.2 44.9 44.6 44.5 44.4 44.3 ...read more.

Conclusion

One way that the experiment could be improved would be to carry it out in a room in which the temperature was always constant. This would prevent the rate of reaction being increased if the room temperature did the same or decrease if the temperature fell. Temperature variation was not great enough in the experiment to have a significant enough effect on the results to alter the final conclusions drawn. Room temperature would only have varied by plus or minus 2?C. This would only have changed the rate of reaction enough to have varied the burette reading by plus or minus 0.5mm3. Other sources of error were caused by human inaccuracies. For instance inaccurate measuring of potato chip size, time and of the various liquids used will have had some effect on the validity of the results. Human error would only have been responsible for a the size of a potato cube being out by approximately plus or minus 2mm3, the timing could only have been inaccurate by plus or minus 1 second and the measurements made of liquids could only have been incorrect by about plus or minus 1ml. These inaccuracies are only large enough to have altered the results by plus or minus 1mm3 and will therefore not have had a large enough effect to change the conclusions made. To help eliminate the effect of human error on the results the tests could be repeated for more than three times. Using the results from a larger number of repeat tests to calculate averages would minimize the effect of mistakes such as inaccurate timing and measuring. To provide additional evidence to support the conclusion the experiment could be repeated with a larger variation in inhibitor concentration. In particular using concentrations of copper sulphate solution lower than 0.2mols to lessen the large gap between the amount of oxygen produced when copper sulphate is and is not present. As well as using lower substrate concentrations the substrate and enzyme concentrations could be increased. This would lead to a greater production of oxygen and make the volume measurements more accurate. ...read more.

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