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To investigate the effect of a change in temperature on the action of enzymes during starch digestion

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Introduction

To investigate the effect of a change in temperature on the action of enzymes during starch digestion Planning An enzyme is a complex protein which acts as a catalyst. As a catalyst it affects the rate of a specific reaction, each enzyme is used in a different reaction. In digestion there are three main enzymes that are used these are amylase, protease and lipase. Amylase is in saliva and helps to break down starch particles into glucose. Starch as a large particle cannot be absorbed into the blood stream in the small intestine as it is such a long particle so it needs to be broken down so that it can be absorbed as glucose. This process starts as soon as possible and so amylase is present in saliva to help break down the starch straight away. The enzyme amylase cannot work when it enters the stomach as the pH levels deform the protein this makes it unusable, but as it is an enzyme it is not used up. Temperature also affects enzymes and each enzyme has an optimum temperature at which it works best at. Enzymes are thought to work according to lock and key theory, as enzyme has to fit exactly to substrate. ...read more.

Middle

Graph 2 shows the rate at which the reaction took place at different temperatures; the rate has been worked out next to the graph and multiplied so that it is easier to comprehend. Graph 1 shows that as the temperature of the starch and the amylase increases the time taken for the amylase to break down decreases. But after a certain temperature the amylase denatures and the time increases. Our interpolated result helped when drawing a best fit line as there were more points to see where the line joined. Graph 2 shows the same analysis as Graph 1 but shows that as the temperature increases the rate of reaction increases, on this graph you can also see that the amylase denatures. The rule of 10�C rise and a double in rate of reaction does not seem to apply to Graph 2. In chemistry there is a rule that with every 10�C rise in temperature the rate of reaction doubles, this does not work with this reaction but might work if a different ratio was used. Amylase is an enzyme these break down large particles into small particles by lowering the energy needed to break bonds. ...read more.

Conclusion

This could have been done more accurately using a light sensor, light source and computer. This way you could stop each reading at the same light intensity and the time taken for each temperature would have been more accurate. For further accuracy an electronic water bath could have been used in which a thermostat controls the temperature of the water and the results would have been not only more accurate but also reliable. I think the evidence that I obtained is sufficient to conclude that the temperature of enzymes does correspond to the rate at which they work. I found that the optimum temperature for this amylase was at about 53�C. As the temperature increased up to this point the rate increased. The rate became smaller after this point as the amylase denatured due to the temperature and was unable to fit to the starch substrate. For further work I would try and find the optimum ratio at which the amylase worked, I would keep the amylase and starch at the optimum temperature but then change the ratios of starch: amylase. I would predict that the optimum ratio was where there was a lot of amylase to little starch, but I cannot support this prediction with evidence. ...read more.

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