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Investigating the effect of temperature on the enzyme amylase.

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Introduction

Biology coursework - Investigating the effect of temperature on the enzyme amylase Introduction Enzymes are vital; they control and catalyse all of the chemical reactions inside living cells. The enzymes speed up reactions, which would not otherwise happen rapidly enough to maintain the essential life processes. Amylase is the enzyme found in our Saliva. It is a catalyst, which works by breaking down substrate into smaller pieces: increasing the surface area, allowing the enzyme to work on the starch quicker and therefore speeding up the reaction. The aim of this experiment is to see how temperature affects the amylase and its ability to effectively break down starch and form maltose. I will be investigating at which temperature the enzyme becomes irreversibly de-natured and at which temperature it becomes inactive. Starch mixed with water on its own reacts very slowly, taking years too react but because we have the enzyme amylase in our saliva the enzymes catalyses the reaction so well that it can break down starch into sugar in minutes or seconds. Variables The variables in the experiment will be the temperature of the saliva and starch solution, the time at which I record the results, the pH of the starch solution and saliva and the quantities of the solutions. The temperature will be the manipulated, Independent variable as this is what I will be changing. The dependant variable will be the iodine solution turning brown indicating when the amylase has successfully broken down the starch, this being the rate of reaction. I will control the pH, the quantities and the concentration of the substances. I will keep the temperatures we choose below 70*c as the enzyme could be denatured (the active site changing irreversibly by the sheer heat) and above 0*c as the amylase would become dormant (not an irreversible change - can become active by being brought back up to its optimum temperature). ...read more.

Middle

tile at zero seconds as it would probably not show results and the iodine show brown at even the optimum pH till well after zero seconds. I still think is relevant with the optimum temperature and it did not seem to disrupt my results last time so I shall do this again. Method I will measure out 5cm3 of a 5% starch solution in a 10cm3 measuring cylinder and pour it into a test tube. Then I will fill another test tube with 5cm3 of dilute saliva solution (2:3 ratio - 2cm3 saliva and 3cm3 of distilled water). Using the pipette, i will then put 3 drops of iodine solution into each of the 'dimples' on the dimple tile. I will put both test tubes into a water bath heated to one of the temperatures I have chosen (20*c, 30*c, 40*c, 50*c and 60*c) so they can come to equilibrium. I shall leave them in there for 5 minutes then mix the two solutions and start the timer as soon as the two solutions make contact. Then, starting at zero seconds, I will pipette two fresh drops of the solution into each dimple with iodine every 15 seconds. I will then stop the timer when the iodine solution turns brown; indicating that there is no starch left in the solution and the amylase has worked and turned it to maltose. If the solution does not turn brown after 10 minutes, I will stop the timer. I will do 5 different temperatures and repeat each one 3 times for reliable results so I can find an average and plot it on a graph and then to see the rate of reaction I will use 1/time to produce a rate graph. I will identify anomalous results and re-do them to get results that are more accurate. I will have a range of 20c to 60c, which is sensible as it should be below de-naturing temperature and above the in-activating temperature. ...read more.

Conclusion

But, as I said before this should not have given me inaccurate results as none of the temperatures, not even the optimum of 40*c showed results that early on. I did not have time to do a repeat so I took other peoples results and this was obviously not as accurate as it would have been had I done the experiment with my own saliva each time as people have different strengths of saliva. Therefore I was not controlling this variable and, had I had time I would have remedied this by repeating the experiment another 2 times to find an accurate average. However this was not possible but despite the anomalous second set of results my results and graph did show the basic idea that in extremes of temperature the enzyme is less efficient. My results are not very reliable as the saliva strength was not controlled as it should have been (I should have repeated with my own saliva) but they are accurate - I did measure everything out carefully with precision and timed to.0 of a second. To improve the experiment I would repeat it with my own saliva. Another thing I would do is let the froth from the saliva go down before measuring it because it was hard to tell where the liquid level was. It would have been a good idea to in a test tube do a sample of iodine solution with no starch present so I could have known exactly what colour to expect the solution to be once I had put the saliva/starch solution in it and the enzyme had catalysed the reaction and the starch had been broken down. To extend the investigation I could test the final solution with Benedict's solution to check if the starch had gone and there was maltose present. Also having seen the effects of temperature and pH on enzyme activity I could do the experiment but this time with the manipulated variable being the concentration to see how that affected the enzymes efficiency ...read more.

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