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To investigate the course of an enzyme controlled reaction

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Jessica Ashton AS Practical - To investigate the course of an enzyme controlled reaction Aim To investigate how the concentration of an enzyme affects the rate of an enzyme controlled reaction, using different concentrations of diastase to see how the rate of reaction is affected. Variables that need to be controlled Variable Why this could affect the experiment How it will be controlled Temperature If the temperature fluctuates, this could easily affect the results because if the temperature gets higher or lower then the enzyme will not work as well as expected at that specific temperature and the test will no longer be fair. This will be controlled by heating both the starch and the diastase solutions in a water bath that is kept at a continual temperature of 35�c. Pressure If the pressure changes this may affect the starch and diastase and how they react together. This is hard to control but the experiment will be carried out at the normal pressure of the room. Volumes of substances used These need to maintain the same throughout the whole experiment otherwise the test will no longer be fair. This can be controlled by using syringes that are accurate to the measurements being used i.e. the smallest syringe for the measurement. For example, I will be measuring 5cm� of diastase so the most accurate syringe I could use is a 5cm� syringe. Concentration of starch This must not change because the variable I have decided to change is the concentration if diastase and two variables cannot change if a fair test us being carried out. ...read more.


Therefore starch concentration will be lower at the end of the ten minutes so the percentage transmission reading on the colorimeter will be higher. I will use a graph to convert the transmission reading from the colorimeter into a starch concentration. When I have these results I can work out the rates of reactions for the different concentrations. So when there is a high concentration of enzyme, more enzyme-substrate complexes will be formed at a faster rate than at lower concentrations. Therefore I predict that the higher the enzyme concentration, the faster the rate of reaction will be. I found information from the following sources: Mary Jones, Richard Fosbery, Dennis Taylor. (2000). Cambridge Advanced Sciences Biology 1. ISBN 0 521 78719 X MSN Learning & Research. Encyclopedia article from Encarta, Enzyme http://www.encarta.com/encnet/refpages/RefArticle.aspx?refid=761575875 Results transmission reading in % at different diastase concentrations (%) time in minutes 0.2 0.4 0.6 0.8 1 0 30 33 27 30 32.5 31 30 30 32 48 41 45 40 42 40 1 38 36 39 49 50 48 62 48 59 70 73 72 72 75 73 2 44 42 49 64 62 59 76 79 69 82 85 83 88 87 86 3 54 55 55 72 69 68 84 84 79 84 89 87 94 96 92 4 64 63 60 81 79 78 92 89 85 92 92 90 94 96 93 5 69 70 65 80 82 83 94 91 90 92 95 93 92 94 95 6 78 77 70 86 82 82 92 90 91 92 95 93 92 95 95 7 70 80 74 84 84 84 92 92 92 92 96 94 95 96 94 8 78 82 78 86 85 ...read more.


When taking volumes of all the liquids used in the experiment I used the smallest syringe for the measurement I wanted to take, this would make any inaccuracies as small as possible. I think the one of the limitations that would have the biggest effect on the experiment would be that of the temperature of the water baths because if the temperature gets higher or lower it would have an effect on the rate of reaction because if the temperature increased then the molecules in the solution would have more kinetic energy so they would more likely to collide with each other and form more enzyme-substrate complexes. If the temperature dropped then the molecules would have less kinetic energy so they would be less likely to collide, so less product would be made. To make this less of a limitation next time I would make sure I used the same water bath and make sure a constant temperature of 35�c was maintained. If this was done there would be a smaller chance of anomalous results. The second of the limitations that would have the biggest effect are the measurements of the volumes. Making sure that all the measurements that were taken were as precise as possible and to make it even more precise, using the smallest syringe for that measurement. This makes inaccuracies as small as possible. To make this better next time I would make sure my measurement taking was as precise as possible and double check it was correct before putting it into any mixtures. Most of these limitations are fairly small and don't have any major effect on the results. Therefore I can say that the limitations and inaccuracies found in the method were not significant enough as to have an effect on my final results. ...read more.

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