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Factors affecting the activity of enzymes Aim: to investigate the factors affecting the activity of enzymes. Factors: The factors that could possibly affect the activity of enzymes are: – Temperature: rate of reaction increases as temperature increases. Concentration of enzyme: rate of reaction increases as concentration of enzyme increases. pH: extremes of pH denature enzymes. Surface area: rate of reaction increases as surface area increases. Inhibitors: if there are any impurities, then they will restrict the rate of the reaction.
Key Factor: I will be using temperature as a variable, and keeping all other factors constant. Therefore, testing temperature as the key factor. Prediction: I believe, that as the temperature of the starch and amylase increases, as will the rate of the reaction. However, once the optimum temperature is reached, the amylase will stop working. Hypothesis: The reason I believe that as the temperature of the starch and amylase increases, as will the rate of the reaction, is because of the collision theory.
The collision theory tells us, that the more the solution is heated, the more the particles inside vibrate. Therefore, if the different particles are vibrating a lot more, it means that they will collide a lot more, and so the reaction will occur a lot faster. So in the case of the experiment we will be doing; the higher the temperature of the starch and amylase, the more these particles will vibrate and collide, and so the faster the amylase will be broken down. I also believe, that once an optimum temperature is reached, the amylase will stop working. This is because, above a certain
temperature, enzymes, being proteins are denatured (change shape), and so can no longer combine with the substances. Fair Test: In order to make this a fair test, the following things must be taken into account: Ensure that the volumes of amylase and starch are constant. Ensure that the pH levels of the starch and amylase are the same. Ensure that all the apparatus are totally clean, i. e. have no impurities. Ensure that the temperature of the solutions remain the same as planned. Ensure that the temperatures of the water baths and ice bath are kept as constant as possible.
Ensure that the starch and amylase solution is kept in the water bath in between each 30-second gap, so as to ensure a constant temperature throughout. Method: Two test-tubes, one filled with 5mg of starch suspension, and one filled with 5mg of amylase solution, are both put into a tub of ice. Whilst these are left inside the tub to cool down, droplets of iodine solution are put in each cavity of the spotting tray. Once the temperatures of the starch and amylase solution have become constant, then they are mixed together, and a droplet of this solution is then added to the first cavity of iodine.
The test-tube is then put back in the ice tub, and then every 30 seconds, another droplet of the solution is added to a different cavity of iodine, until the purple colour that should appear, has disappeared. The time taken for the purple colour to disappear, is then recorded. When the purple colour disappears, it means that the amylase has totally broken down the starch. The same process is then repeated, but in water baths, with temperatures of 30? C, 50? C, and one is also done in room temperature. Everything is then repeated once more, and the average times for each temperature are calculated.
Diagram: Apparatus: The following apparatus will be used in the experiment: 3 water baths tub pipette 2 syringes 2 beakers 2 test-tubes spotting tray thermometer test-tube holder Results: Temperature (i?? C) 0i?? C 20i?? C 30i?? C 50i?? C Time Attempt 1 450secs 270secs 180secs 210secs taken for Attempt 2 480secs 300secs 180secs 210secs starch to Average 465secs 285secs 180secs 210secs disappear 1/T 1/465secs 1/285secs 1/180secs 1/210secs Graph: Conclusion: To a certain extent my hypothesis was correct, but there still were some unforeseen results.
For example, I mentioned in my hypothesis that as the temperature of the starch and amylase increases, as will the rate of the reaction. As the graph shows, the rate of reaction did increase as the temperature increased, but only to a point; after 30? C, the rate of reaction began to decrease. However, in my hypothesis, I mentioned that once a high enough temperature is reached, the amylase would stop working. This of course was incorrect, because once it reached 30? C, the amylase did not stop working, it just became less efficient.
One thing I noticed whilst looking at the results table, was that as the temperature increased by 10? C, the rate of reaction doubled. This would explain why the graph increases steadily at the beginning, and then starts to steeply increase. Errors and Improvements: Some of the results may have been inaccurate, due to the 30-second range in between each time another droplet is added to a cavity of iodine. This could have been improved upon, by making it only a 5-second range for example, because the exact time when the starch disappears would be closer to the time recorded than with a 30-second range.
An example as to why a couple of the results may not have been proportional, is when the starch and amylase were put in the ice tub. It is very unlikely that the solutions would have reached 0? C and remained constant. This could have been improved upon, by putting the solutions in a freezer instead, because it would keep to the same temperature throughout. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.