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Investigation to determine the effect of substrate concentration on the rate of breakdown of hydrogen peroxide by the enzyme catalase.

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Investigation to determine the effect of substrate concentration on the rate of breakdown of hydrogen peroxide by the enzyme catalase. Aim: To investigate the effect of substrate concentration on the breakdown of hydrogen - peroxide by the enzyme catalase. Introduction: Enzymes are protein molecules and they can be found in living cells. They are biological catalysts, and their function is to speed up reactions within each cell. Each enzyme will only catalyse one reaction, as they are very specific. Catalase is an enzyme. It is a protein molecule and it is found in food like potatoes, liver and celery. It can also be found in yeast. Catalase catalyses the reaction of hydrogen-peroxide into water and oxygen. Its function is to remove hydrogen peroxide from cells. The equation for this reaction is 2H2O2 --> 2H20 + O. This type of reaction is called an catabolic reaction. This reaction is important as it breaks down hydrogen peroxide, which is a poison, into oxygen and water which is harmless. Hydrogen Peroxide is the poisonous waste product of metabolism and its needs to be broken down. The un-catalysed breakdown of hydrogen-peroxide is slow, so dangerous amounts of the toxin would build up. However, when the breakdown is catalysed by catalase, the reaction is much faster. Catalase is able to speed up the decomposition of hydrogen peroxide because the shape of its active site is complimentary to the shape of H2O2. At body temperature the turnover rate for one molecule of the enzyme is 6million per second. ...read more.


From the data obtained from this experiment a graph would be plotted, with the concentration of H2O2 plotted on the X-axis and the rate of reaction plotted on the Y-axis. In this case, the rate of reaction is going to be volume of O2 collected per minute. When we measured the volume of O2 we took the reading from the bottom of the meniscus, and we took the reading at eye level as well. To ensure that the experiment is carried out as fairly and as accurately as is possible, all other potential variables must be identified and steps must be taken to ensure that they are kept the same, or as close as can be possible in a laboratory. Variables that must not be altered include: Temperature, Concentration of catalase, Volume of catalase, Volume of hydrogen peroxide, Pressure, pH. To keep every other variable the same, a value needs to be decided for each of them. The reaction will be carried out at room temperature, (approximately 21 c) as this will not change significantly during the course of the experiment. This will be the best temperature to carry out the investigation at, as during the pre - testing at higher temperature than room temperature the reaction is to fast to accurately measure. Also, if we were to carry the experiment out at a temperature above room temperature, we would need to keep that constant and it would be impractical to do so. The volume of the catalase will be easy to keep constant, we are using 2cm3 of catalase and this will be measured using a 2cm3 syringe. ...read more.


Evaluation: The results that were obtained in this experiment were quite accurate. The data that was obtained was quite accurate except for the value for 20 volumes. This result was higher than was expected, but this could be due to a number of reasons. The volume of the either the substrate or the enzyme may have been slightly over measured. The result of this would have been that the rate of breakdown of hydrogen peroxide would have stayed faster for slightly longer, increasing the volume of oxygen collected. At the same time, the delivery tube may have been removed slightly after 10 seconds. This would have led to more oxygen being collected. This error would then have been exaggerated further, as when the graph was plotted the volume of the gas was taken as cm / per minute. To get this value the result had to be multiplied by six, so the error would have increased by a factor of 6. If this experiment was to be carried out again, I would measure more concentrations of hydrogen peroxide. Instead of measuring 20, 16, 12, 8, 4 and 0 volumes, I would instead measure 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, and 0 volumes. However, the results obtained from the experiment prove that the concentration of the Hydrogen Peroxide does affect the rate of its breakdown. The experiment itself was carried out in such a way it was possible to obtain the most reliable results. The stop clock was started as the hydrogen peroxide was introduced to the catalase, and after 10 seconds, the test tube was removed from the delivery tube. ...read more.

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