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Experiment to study the effect of Changing enzyme concentration on the rate of catalase action.

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Background A definition of an enzyme is a biological catalysts; proteins made by living organisms, which speed up a chemical reaction. Catalysts enable substances to react more easily. They do this by helping bonds break between atoms to break and form more easily. The particles need less energy to react, so the reactions proceed more quickly. Enzymes are biological catalysts this means that they speed up reactions that would normally occur quite slowly. Enzymes are used to break down substances and are used in many metabolic processes such as digestion. Chemical reaction takes place all the time in living organisms and the enzymes that are present in the cells make the reaction occur much more quickly. Chemical reactions involve one substance changing into another. The substance that is begun with is called a substrate and the substance made by the reaction is called a product. Enzymes change their substrate to products: e.g: Enzyme Substrate The product Catalase Hydrogen peroxide Water + oxygen Amylase Starch Maltose Maltase Maltose Glucose Protease Protein Amino acids Lipase Lipids Fatty acids + glycerol Enzymes are made up of protein, and have a precise 3D shape. On there surface is an active site or a dent, which is of a very specific shape. It is exactly the rite size and shape for a molecule of the enzymes substrate to fit into. Each enzyme has its own shape or active site, which will only fit together with its own substrate (chemical). When the substrate molecule fits into the active site the enzyme 'tweaks' the substrate molecule making it out of shape and so breaking it into product molecules. These products leave their active site, which are ready to do the same thing to another substrate molecule. The lock and key process More enzyme therefore greater activity because there are more active sites. The substrate we are studying is hydrogen peroxide and its enzyme catalase. ...read more.


temperatures may increase due to the number of people in the lab, so windows may need to be opened when needed as there is no way of keeping this constant, the temperature should be monitored to explain any anomalous results. > The temperature of the solution should remain the same - there is no way of keep this constant either and so will also b monitored. > The pH should be kept constant - there is no way of keeping this constant, so we can keep a record the pH through out the experiment to see if there are any changes which could be accounted for anomalous results. > The volume of hydrogen peroxide should be the same for all the different surface areas - To control the substrate concentration; identical quantities of the substrate should be used for each reading. To ensure that this is measured precisely, 20ml syringes will be used to accurately gauge to exact quantities. If any of these are not kept constant then it will not be a fair test, as they will affect the rate of catalase action. The independent variable > This is the surface area of the chips, which is the enzyme concentration i.e. the amount of enzyme available. I will vary the enzyme concentration by altering the number of pieces of potato that contain the Catalase, in the reaction. The dependent variable > This is the number of oxygen bubbles produced per minute from the reaction, which is the rate of catalase action. Diagram of apparatus I produces a table in advance, so that I could record my results easily and beable to read them afterwards. Number of pieces Of Chips Surface area Number of bubbles Average number of bubbles (Per minute) pH Room temperature �C Solution Temperature �C In 5 minutes Repeat Preliminary experiment This is an experiment that is done before hand in order for me to know much hydrogen peroxide to use throughout the experiment and how long I should kept the length of the chips. ...read more.


Another reason could be that as there was a larger surface area and the capacity of the test tube was not sufficient enough so the distribution of catalase may not have been constant. Some of the pieces of potato may have been over lapping each other and therefore the hydrogen peroxide was not able to attack all the sides of each chip. The plateau may also have occurred because as the chips were cut into more pieces and the surface area increased the pieces became smaller and lighter and so sticked to the sides of the test tube rather than mixing with the hydrogen peroxide. Evaluation I feel that this experiment worked reasonably well and to my expectation, because I got a reasonable set of results, which proved my prediction to be correct and enabled me to establish a firm conclusion. I think that my results were accurate enough, for the experiment as they produced a graph and conclusion, although I do feel that if I had a larger range of surface areas, say from it would make my results more reliable. Nevertheless they are still more or less accurate. The method used was the best way of carrying out the experiment, because it was the most simple and easiest way of doing so and as it worked well. It also gave me encouraging results, although I could have carried out the experiment out in a much more reliable and accurate way, which would improve the reliability of my results. I could improve the method of the experiment in many ways. In this experiment, the pH was kept constant using a pH 7 buffer, selected to maintain a pH level suited to the enzyme by being equal to the natural environment of the enzyme (potato tissue). This was achieved by using a test tube rack and tongs to handle the apparatus so that the heat from my hands did not affect the catalase. They should not have affected this investigation, however, as none were added. ...read more.

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