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Factors that affects the rate of breakdown of a substrate by an enzyme

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Introduction

1. Aim In this Investigation, I intend to study the one of the several factors that affects the rate of breakdown of a substrate by an enzyme. In this case, I shall be investigating catalase in yeast, and how it breaks down Hydrogen Peroxide. Enzymes exist in all living things. They are composed of polymers of amino acids and are produced in living cells. Each cell contains several hundred enzymes, which catalyses a vast number of chemical reactions. Enzymes are known as Biological Catalysts as they dramatically increase the rate at which reactions occur within living organisms, without being 'used up' or effecting the reaction in any other way. Enzyme catalysis saves the need for an increase in temperature in order to speed up reactions within living things. Such an increase in temperature could be lethal to the organism. Enzymes are specific - they only control one type of reaction; therefore, I must use one specific enzyme in my experiment, to find a clear way of measuring the rate. All enzymes work in similar ways, and have similar properties. They are all globular proteins and biological catalysts. They increase the rate of a reaction without being used up, and their presence does not change the nature of a reaction or the end product. Enzymes work by having an active site, made from amino acids. At this location a substrate molecule will bind with the enzyme and a reaction takes place. The enzyme itself is not affected and it releases the new chemical after the reaction. After the release, more substrate molecules can bind with the active site. I have created the diagrams shown below, to displaying the 'lock and key' enzyme/substrate reaction. 2. Factors In this investigation I intend to explore one of the factors that affect the rate of enzyme catalysis. My research from textbooks and Internet searches suggests that this depends on several factors; temperature, volume, pressure, pH and concentration. After research and careful consideration, I have decided to investigate concentration. ...read more.

Middle

Repeating the experiments several times help to produce better and more accurate results, and any inaccuracies in one experiment, will be compensated for by other experiments. I shall record the results in a table such as the one below: Hydrogen Peroxide Concentration (%) 0 4 8 10 12 16 20 Time Taken (s) Test 1 Time Taken (s) Test 2 Time Taken (s) Test 3 Average of Tests Rate I have decided to calculate the rate too, as this would enable me to draw a conclusive graph. The rate can be calculated by: Rate = 25/Average Time (s) This will give the rate of Oxygen produced per second, because I calculated the time taken to collect 25cm3 of Oxygen. I will make sure the conical flask is thoroughly washed out and dried so that there will be an exact amount of water/peroxide. If I do not do this, it will be an inaccurate investigation. I have to also note that for safety, the maximum concentration of Hydrogen Peroxide available to me is 20%. Safety is paramount in this experiment, as higher concentrations of Peroxide could harm the skin. However, even at this concentration, Peroxide will be corrosive to benches, and more importantly eyes. If it makes contact with the benches or my skin, I must cleanse it off immediately. To prevent it from entering my eyes, I shall wear safety specs or goggles. * After I performed the first experiment, I realised a fault in my method. When I inserted the yeast via the syringe, I found that not all the yeast was transferred into the conical flask. Therefore, after I sucked up the yeast into the syringe, I removed the end from the beaker of yeast, and carried on pulling on the end, so that the plastic black end met the '10 ml' mark. This left me with air behind the yeast. Therefore, when I inserted the yeast, the extra air helped to push ALL the yeast in. ...read more.

Conclusion

They do not change the conclusion of my results, and are only slightly irregular, so I think that they are due to experimental error on my behalf. Apart from these, I have only one other anomalous results: Test 3 in the 12% experiment. This was quite far off from the other two, so I repeated the concentration again, and took the average excluding the anomaly. 4. To improve this experiment, I would do several things. a) I would have another person, as a helper. This, I think, would eliminate the problem of inaccuracies regarding the starting of the stopwatch. b) Rather than collecting the gas in a test tube of water, I would collect it in a gas syringe. This would cancel a need for a clamp and stand, and also make reading off the amount of gas collected easier, getting rid of some inaccuracies. c) Rather than use yeast as a source of catalase, I would use catalase itself in its pure form. This could be a more accurate way of obtaining conclusions and untainted results. d) The experiment could be repeated more times to help get rid of any anomalies. A better overall result would be obtained by repeating the experiment more times because any errors in one experiment should be compensated for by the other experiments. e) Using more concentrations of Hydrogen Peroxide would have produced a better looking graph, which would be more accurate. 5. As extensive work, I would like to use concentrations higher than 20% to extend the graph so that the maximum possible rate of reaction could be reached. Also, to let me get a better picture of how substrate breakdown by an enzyme is affected by substrate concentration, I would repeat the same experiment, with a different enzyme, and therefore, a different substrate. I would be able to see if the same conclusions can be made. This document was downloaded from Coursework.Info - The UK's Coursework Database ?? ?? ?? ?? K Logishetty Planning 1 ...read more.

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