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Investigating the effect of pH on the hydrolysis of starch by alpha amylase.

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Investigating the effect of pH on the hydrolysis of starch by alpha amylase Planning a: Research question: The aim of this experiment is to investigate the effect of pH on the hydrolysis of starch by alpha-amylase. Hypothesis: Starch is broken down by en enzyme, the enzyme amylase. Enzymes are defined as biological catalysts, which speed up a reaction and make it more likely to happen. They are very specific for each reaction they catalyse, which is called enzyme specificity. Every enzyme molecule has an active site into which a substrate molecule fits in perfectly. At the end of each reaction the enzyme is broken down into 2 products, in this case starch is broken down by amylase into maltose. This mechanism is called the lock and key hypothesis. The pH is one of the factors that affect the rate of a reaction. There are other factors like temperature, substrate concentration and enzyme concentration. I will summarise their importance shortly. If there is an increase in temperature the reaction will also increase. The reaction rate will rise up to the temperature where it works best, which is called the optimum temperature. ...read more.


mixture, and mixed well by shaking. Immediately a sample will be taken and placed into a tile. This will be continued every 30 seconds and for minutes. After 5 minutes samples will be taken only every minute. Supposedly twp tubes will be run at the same time. The process will be continued for twenty minutes if necessary. Meanwhile the experiment has to be started with other tubes, otherwise there will not be enough time. It is important to rinse the pipettes after each experiment. If the different pHs would mix the pH concentration would change it this would severely affect the results. After each experiment the time it took the reaction to end will be noted. The reaction will have stopped when any blue/ black colour disappears, this will signify that the starch has broken down completely. Data processing and presentation: Tube Time it took the reaction to end Rate of reaction 1/sec pH 1 170 0.00588 pH 2 80 0.0125 pH 4 120 0.00833 pH 7 140 0.00714 pH 9 90 0.0111 Data analysis: When referring to graph #2 and checking the results for pH 1 the hypothesis seem to be correct. ...read more.


Conclusion and evaluation: Overall the experiment was conducted as described in the method. But I cannot really accept my hypothesis, because the was nor a constant increase in the reaction rate nor was the reaction working best at the neutral pH of 7. As I said before we did not use a stopwatch to measure the time, instead a normal wall clock. I believe that this did affect the results in some way. We tried to measure the time accurately but sometimes we forgot the time were we had started or during the 30 seconds we were filling tiles with iodine solution instead of paying attention to the time. To improve the results time should measured accurately with a stop watch. In addition enough tiles should be filled with iodine solution. Another factor which probably influenced the result heavily was that the dropping pipettes were either not cleaned properly or not rinsed at all. Also it could be that the reaction rate had stopped before or between the 30 seconds, so it is hard to get the right time. Due to the fact that we got such unexpected results for the pH concentration of 7, we did the experiment for this concentration again, next time to approve or improve the results the whole procedure should be repeated. ...read more.

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