Method
8 samples of potato tissue were taken with the cork borer, and then these were measured to 1.5cm each. 8 test tubes were labelled – 2 for the ice, 2 for room temperature, 2 for 40º and 2 for 60º. The 40ºC and 60ºC test tubes were then placed, with the potato samples inside, into their respective water baths. The 2 ice test tubes were placed in a beaker filled with ice, while the 2 room temperature test tubes were left out. These were all left for exactly 2 minutes, then removed and placed in the test tube rack. Then 5cm³ of hydrogen peroxide was added to each, and then 10 drops of detergent. The 2 room temperature test tubes were left in the rack (as it was obviously room temperature in the lab) while the 40ºC and 60ºC tubes were placed back in the respective water baths, and the ice test tubes were put back into the ice beaker. They were all left for exactly 5 minutes, and then were removed. They were all placed back in the test tube rack, and then the level of froth in the tubes was measured using the ruler. The results were all recorded.
Results
Ice Room 40ºC 60ºC
Temp.
Conclusion
From our results, we can conclude that the optimum temperature for catalase activity with hydrogen peroxide is room temperature, which is between 20-23ºC. Under these conditions, the height of foam was 7.2cm, then 6.9cm (an average of 7.05cm). This shows that catalase functions well at this temperature and reacts rapidly. At the temperature of ice (around 2ºC) the height of foam was 3.8cm and 4.6cm (average 4.2cm). This is because the temperature of ice is below the main working range of enzymes (around 5-40ºC) so the catalase cannot break down the hydrogen peroxide properly. At 40ºC, the heights of foam were 6.4cm and 5.9cm (average 6.15cm). The catalase functions well at this temperature, but not quite as well as at room temperature as it is almost outside the working range of the enzyme. At 60ºC the levels of froth are the lowest of all – just 1.9cm and 1.7 (average 1.8cm). This is because the temperature is too high for the catalase to function. It is outside of the working range of the enzyme and the catalase becomes denatured. Enzymes are easily damaged by heat, so this low level of catalase activity is due to the high temperature. So overall we have proved that the optimum temperature of the range provided was room temperature (around 20-23ºC), while the working range for catalase is 5-40ºC. Any temperature above or below this will have little enzyme activity.
Evaluation
This experiment was well carried out but there were a number of changes that could have been made to safeguard against possible sources of error. One possible source of error was timing – the beakers containing the potato tissue and hydrogen peroxide may have been exposed to certain temperatures for too long or too short a period of time, so the enzymes would not have reacted as they would normally. The solution to this would have been more careful and accurate timing to make sure of the validity of the experiment. There was also a chance of too much detergent being used – 10 drops is not a very specific measurement. It would not have been difficult to measure out the amount required to make sure the test was fair. If too much detergent had been added there would have been a greater level of froth making it appear as though the enzymes had reacted more rapidly, when that would not have been the case. Another possible improvement to the experiment would have been to add more repetitions – two were not really enough to be certain to be sure of the results. One freak result would have completely skewed our results. Adding more would have enabled us to disregard a freak result. We could also have increased the range of temperatures to help us gather a wider range of results. This would have made it possible for us to find the optimum level of catalase activity more accurately and gauge it more finely. Since our two best temperatures for enzyme activity were 20ºC and 40ºC another temperature between these two (presumably 30ºC) would have helped us to obtain the optimal temperature more precisely and it would have made our results more conclusive. Apart from these possible improvements this investigation was carried out well.
