To investigate how varying the temperature of the reaction between amylase and starch affects the rate of reaction.

Safety

• Goggles will be worn at all times during the practical part of the experiment
• Hair will be tied back if necessary

Fair test

Each time I will be using 5mls of starch and 2mls 1% amylase solution, to ensure that the same amount of each substance is used throughout.

Predictions:  What will happen at the different temperatures?

In this experiment, I will be using the temperatures 0˚C, 10˚C, 20˚C, 30˚C, 40˚C and 50˚C.  I predict that the rate of enzyme activity will be slowest at 0˚C, because the substrates have less energy and will not collide with the enzyme as often and the collisions will not be as powerful.  Therefore less starch will be broken down.  As the temperature increases to 10˚C and 20˚C I think that the reaction will be faster as there is more energy.  The rate of reaction will sharply increase up to about 37˚C - 40˚C, at which point the amount of activity will be the highest, and the iodine will turn to a light-brown colour in the shortest time.  After this point, I think the rate will start to decrease because the enzyme is being altered by the heat and starting to be denatured.   This is because enzymes are proteins, and the active site will change shape as the heat gets too high.  At this point the substrate wont fit in the enzyme and less reactions will occur.

Results

The results show that the reaction was too slow to be recorded at 0˚C, and became faster until it reached 40˚C, where it reached the optimum temperature at which the enzyme works.  At 50˚C the reaction was becoming slower because the enzyme was starting to become denatured.

Analysis of graph

There is a steady curve which shows that the enzymes were working faster as the temperature increased.  However, the curve rises again at 50˚C which shows that less starch was being broken down.

Conclusion

From my set of results and graph, I can determine that my prediction was right.  The amylase was breaking down more starch as the temperature increased because there was more energy present.

Evaluation

Overall, I feel that I gained the results I was hoping for at the start.  There was a pattern that could be seen in the results, and the graph showed that there were no anomalous results.  There was always the chance, though, of making a mistake in this experiment.  The interpretation was left to human error as I had to judge when I felt the experiment had finished.  I also had to try and make this judgement constant for each temperature, which is almost impossible.  That is why, if I was to do the experiment again, I would use a log-it to record the amount of light getting through the iodine after the mixture had been added to it, which would then enable me to reach the end of the experiment at the same point each time.  This eliminates the room for human error.