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Investigating the effect of enzyme catalase concentration on hydrogen peroxide.

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SC1 Plan INVESTIGATING THE EFFECT OF ENZYME CATALASE CONCENTRATION ON HYDROGEN PEROXIDE. PLANNING. Background Information: Firstly it must be established that enzymes are protein catalysts. The definition of an enzyme is that it takes part in a chemical reaction but still remains intact after the reaction and is hence not spent. There are two types of enzyme reaction, these can be separated into catabolic and anabolic, anabolic reactions involve growth (i.e. photosynthesis) whereas catabolic reactions involve an enzyme breaking down a substance, for example digestion where organic compounds are broken down in respiration. One thing that all these chemical reactions have in common is that they take place in aquatic conditions. Enzymes have active binding sites, which will fit only certain substrates and thus, they are said to be substrate specific. Enzymes are not destroyed but merely denatured at certain temperatures or by certain pH levels. Temperature denaturisation takes place at temperatures above 60�c but in certain human enzymes it is 45�c. Most enzymes will work at optimum efficiency at around pH 7, which is considered neutral. At a certain or pH the active site of the enzyme may have been changed in shape, this change is likely to be irreversible, however, after the pH changes the enzyme can be reversed back. If the temperature is increased without exceeding the denaturisation barrier, this can lead to an increase of kinetic energy in the reaction between the substrate and the enzyme molecules, this can be explained as resulting in a greater collision rate, this speeds up the rate of the reaction. An accepted figure for this rate of increase is that for every 10�c gained; this results in the reaction rate doubling. Also, by increasing the enzyme or substrate quantity, this may result in the increase of the reaction rate as more collisions take place in less time. The enzyme catalase is present in all living tissue. Catalase breaks down the chemical Hydrogen Peroxide (H2O2) into the harmless chemicals Water (H2O) and Oxygen (O2). ...read more.


Results: Results Table. Size of potato strip Bubbles given off in first minute Bubbles given off in second minute Average quantity of bubbles given off in first minute Average quantity of bubbles given off in second minute 2 4 3 4 3.5 4 10 8 10.5 8.5 6 20 14 21 14.5 8 22 16 22 14.5 10 19 14 18 13.5 12 28 18 28 19 Results. At the beginning of the experiment the room temperature was noted to be 19�c and the pH was 6. After the hydrogen peroxide was added, the liquid began to show signs of activity in frothing and bubbling, this was an obvious sign that oxygen was being produced and this was confirmed by the produced oxygen appearing in the form of bubbles at the end of the delivery tube and into the 10ml of water. If there had been more time for the experiment it is likely that there would have been no hydrogen peroxide but merely water since it would have been catabolically broken down into two natural substances, well known by man, oxygen and water- produced by catalyse enzymes breaking down some potato cells. More specific results are shown in the tables above. Number of potato discs Time taken for first bubble to emerge for first reading (secs) Time taken for first bubble to emerge for second reading (secs) 2 55 52 4 39 35 6 20 25 8 30 36 10 27 25 12 19 17 Analysing Evidence. From the graph it is possible to see that between 4-8 potato discs the number of bubbles produces increases from 9 bubbles produced on average in two minutes to 19 bubbles on average in two minutes by 8 potato discs but the shape of the graph suggests that from 8-10 the number of bubbles produced begins to drop but then suddenly rises. Thus, it would be possible to make a potential conclusion that the dependent variable begins to increase as the independent variable increases and then ...read more.


For my purposes, I believe that my results were accurate but I would not base any further scientific experimentation on merely my results but maybe culminate more to find an average. My first concern about this experiment is that by taking all the readings from one source of potato, it is possible that the potato I took my readings from was defected and so all my readings will be from an impure source which may have been catalyse deprived or abnormally catalyse rich and so I would repeat the same experiment but with two sources of potato just to ensure that the readings are similar for potatoes since I have no justification that my potato is the stereotypical potato. I would also use more complicated apparatus since the apparatus is simple and easy to use but it would be possible to find a point to sacrifice complication for improving the accuracy of one's readings. I felt that the experiment could have been kept in a temperature bath just to ensure that the temperature was constant throughout since from the background information I learnt that enzymes are affected by temperature. Also, although I carried out a pre-investigatory trial to decide and help to plan a method I would have preferred to do another one just to confirm any variables for my ultimate experiment. I believed that the range should have been extended but on the other hand one had to take into account human resources and time. I believe that the results were slightly limited due to time and the surface area was affected due to the lack of space in the boiling tube and so this would have affected the experiments results. Thus, the range should have been extended in order to see the shape over more readings and I would have liked to taken each reading over more time just to see the effect. Thus, the recommendations in the paragraph are the ways in which I believe that the experiment could be improved for anyone doing the experiment. ...read more.

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