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Investigating the Rate of Reaction In Enzymes

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INVESTIGATING THE RATE OF REACTION IN ENZYMES Robert Smith Our aim is to investigate the factors that affect the rate of reaction in enzymes, in this case amylase, and its substrate: starch. To investigate this there are three possible variables that should be considered: * Temperature, * pH, * Concentration. I have chosen to do temperature as I feel that I can do this experiment the most effectively and know more about temperature in relation to enzymes than the other two variables. Some enzymes behave/react differently with their substrate at different temperatures. Amylase reacts optimally at quite high temperatures; above 50 degrees Celsius. Below that, as the temperature decreases, the rate of reaction slows. This is because the lower the temperature the slower the molecules move around in the mixture of enzyme and substrate solution. This means that there is less of a chance of a substrate molecule coming into contact with and enzyme molecule than if they were moving faster. So the higher the temperature the faster the molecules move around so the higher the chance of the 'lock and key' or enzyme and substrate coming into contact with each other so the faster the reaction. However, at a certain temperature somewhere above 50 degrees Celsius the enzyme will denature and the substrate will no longer fit into the active centre of the enzyme so the rate of reaction will slow to a stop above a certain temperature. ...read more.


I have decided that to make this investigation reliable and to have a decent set of results to analyse at the end that I should take five sets of different temperature results. The diagrams below show how I plan to conduct my experiment in relation to the apparatus listed previously. The following table displays the results obtained from the preliminary experiment. To get a better impression of what the results mean I have plotted them on a graph: The graph shows an obvious negative correlation when a line of best fit is drawn. This means that the higher the temperature the faster the reaction took to finish. I decided not to take more than one reading for each temperature because all I needed was a rough idea of whether or not my method worked. From these results you can't tell where or if the enzyme denatures. This is because the temperature range I used didn't go up quite high enough, so in the main experiment I will have a temperature range that includes a higher top temperature to try and discern when the enzyme denatures. I will also take a wider temperature range. Seeing as how this preliminary experiment worked well, looking at the results I obtained, I will use this same method for the main experiment, repeating each experiment reading twice. ...read more.


The pH was controlled because every substance used in the investigation was taken from the same source. The concentration was controlled because each batch of starch and amylase was measured accurately before mixing. I can't think of any way that the rate of reaction may have been affected, other than by varying the temperature, which was intentional. The results were indeed accurate in relation to each other as two repeats of each individual temperature experiment were made to ensure maximum accuracy. The reaction completion times were all quite close together, implying an accurate procedure as the results were not spread all over the shop. The control I conducted clearly showed that the amylase was the only catalyst of the biochemical reaction that turned the starch into maltose. If I had to repeat this investigation I would take an even wider range of temperatures into account to encompass the denaturing point of the enzyme because this is an important part of investigating how temperature affects the behaviour of the enzyme. Because I feel that otherwise the experiment went well and the method was foolproof, I would follow the same procedure and use the same variable and use the same equipment. If I had had more time I would have liked to have looked at more/different variables and looked at different enzymes and their substrates and see how the variables affected their behaviour as well. ...read more.

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