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Investigating a factor that affects the rate starch is digested by Amylase.

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Introduction

Investigating a factor that affects the rate starch is digested by Amylase Factors that affect the rate of digestion: > Temperature affects the rate of digestion because most enzymes have a specific temperature that they work best at. This is usually body temperature for body enzymes. > pH affects the rate of digestion because most enzymes have a specific pH level at which they work best. > Concentration of substrate affects the rate of digestion because the more concentrated the substrate, the slower the rate of digestion will be for a constant amount of enzyme. This happens because there is too much substrate for the enzyme to digest quickly. > Concentration of enzyme affects the rate of digestion because the more concentrated the enzyme, the faster the rate of digestion will be for a constant amount of substrate. This happens because there are more enzymes available to digest the substrate. Aim: I am going to investigate how pH affects the rate that amylase digests starch. Prediction: I would expect that the rate of reaction between amylase and starch would be higher when it takes place at around pH 6. I think this because in the human mouth, the saliva is slightly acidic, pH 6. In the body, a delicate balance needs to be maintained between the optimal pH for each of it's many enzyme reactions. The pH an enzyme prefers depends on the enzyme itself. Enzymes work on substances called substrates. These react with the enzyme on part of the surface of the enzyme. ...read more.

Middle

The remainder of the experiment is exactly the same process that I followed in my preliminary work. Every 30 seconds, I will use a pipette to remove 3 drops of the solution and add it to a well in the spotting tile. I will do this until the iodine in the spotting tile ceases turning blue/black and remains its original colour. This is when I will stop the stop clock. This process will be repeated for each different pH level. Because I am performing exactly the same experiment for each pH, I can compare the results fairly. Method: I carried out the experiment explained above, exactly as planned. Due to my preliminary work, I had already identified any problems and overcome them when it came to collecting the results for my main experiment. The only problem I encountered was when I performed the tests for starch with an extreme acidic or alkaline solution. I found that at these pH levels, the amylase took a very long time to digest the starch. Because of this I have not obtained results for pH 3 and 9. To ensure the accuracy of my results, I performed the whole experiment three times. The results from all of these trials are presented in the results table. If found that the room temperature was constant for every reading, making it fair to compare the results because they were carried out under the same conditions. Diagram: Results: pH Temperature (?C) Time Taken (minutes) Trial 1 Trial 2 Trial 3 Trial 1 Trail 2 Trial 3 3 22 22 No change after 12 minutes - - 4 22 22 22 7.30 8.00 7.30 ...read more.

Conclusion

Because I have to judge, for each case, whether the iodine has stopped changing colour or not, they may not be consistent. Because of this chance for human error, there was always a panel of three people to determine the results. This means that it is not just my opinion and is the best way of conducting this experiment, as there is no other way. As a further line of investigation, I would like to look at one of the other factors listed on page 1. Temperature is a similar factor to the pH levels, in that each enzyme also has a specific temperature at which it works best. I would use principally the same method as I did to investigate the best pH levels. The several things I would alter are; the pH would always be 6 as I now know that it produces the fastest digestion rate and I would also have to perform the entire experiment using a water bath to heat the test tube and its contents. The water bath could be set to heat the chemicals to a certain temperature so it is the best way of changing the temperature. All the factors that I kept constant in the pH investigation, would also be kept constant in this experiment, except that I would now keep the pH constant at 6. This time it would be the temperature that changes instead of the pH. I would aim to test temperatures varying from 10?C to 90?C. After performing a preliminary investigation for the temperature, I would be able to establish whether this temperature range is suitable. I would also know by how much to increase the temperature each time, or how accurate I want the best temperature to be. 7 1 ...read more.

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