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"An investigation to find out the optimum temperature for the activity of Lipase".

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"AN INVESTIGATION TO FIND OUT THE OPTIMUM TEMPERATURE FOR THE ACTIVITY OF LIPASE" * AIM To investigate the effect of temperature has on enzyme activity and the hypothesis that there is an optimum temperature for the activity of the enzyme lipase. * INTRODUCTION Enzymes are catalysts made up are protein molecules, usually with a globular structure. They accelerate chemical reactions in organisms that would otherwise occur to slow. (Green, Stout, Taylor, 1991) Lipase is a digestive pancreatic enzyme which works to hydrolyses fats into glycerol and fatty acids. (Simpkins, Williams, 1987) These products will react with the Sodium Carbonate (put into the mixture to raise the pH) and in effect lower the pH level towards a more acidic content. This pH change can be observed by using the indicator Phenolphthalein, which changes from a pink colour to colourless at a pH below 8.3. * HYPOTHESIS Lipase is an enzyme found in the human body and from knowledge of human enzymes I expect the optimum temperature to be around 40�C. ...read more.


Phenolphthalein is flammable, keep away from naked flames * RESULTS Below is a table of the times it took for lipase to convert enough fats into fatty acids and glycerol to lower the pH below 8.3 so that the indicator would show this. Start Temp (�C) End Temp (�C) Time Taken Rate of Reaction (g/s) 80 76 No change after <25m 60 54 11m 25s 5.3 40 35 11m 35s 5.2 20 20 20m 38s 2.9 21 21 18m 34s 3.2 If the results are put into a scatter graph (below) and a polynomial trend line added you can see the rate of reactions in comparison. At 20�C we can see the lowest ROR at 2.9 g/s, next is the control experiment which was carried out at room temperature 21�C and the ROR was slightly higher at 3.2 g/s. At 40�C the rate of reaction increase noticeably up to 5.2 g/s as the time taken was nearly halved. At 60�C there was a slight increase in ROR than previously with the time taken only slightly quicker. ...read more.


As the kinetic energy increases the lipase molecules starts to vibrate more. At a certain point this vibrating becomes too great and the weak hydrogen bonds that hold the proteins into its structure begin to break. These breaks result in the lipase's structure shape changes, which changes the shape of the active site. With a different shaped active site the substrate will be not fit into it and will no longer be able to form complexes with it. (~~~~~~~~~~) (See fig1) However the ROR is still higher than for 40�C, which shows us that some of the lipase reacted with the fat before it started denaturing. This is because at the rate of denaturing increases as the temperature increases. Denaturing usually takes place in human enzymes between 40�C and 45�C and this can be seen in the graph as ROR begins to slowdown increasing around 40�C. At the top temperature of 80�C there was no change detectable due to the large amount of kinetic energy subjected to the lipase and it had become denatured. There would have been a little amount of reactions taking place but not enough to lower the pH so that we could observe a change. * CONCLUSION ...read more.

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