The first part of the experiment involves cutting the pieces of liver to the same sizes so that there would be equal amounts of catalase in each. Each piece will be about 1.1 grams. That is the chosen weight that I have chosen since it is a reasonable mass. Then I will create 2 water baths, one for hot temperatures, and one for cold. The cold one will consist on water with different amounts of ice added to get the right temperature. The second one, (the hot one) will be a beaker of water on top of a tripod and wire gauze, with a Bunsen burner underneath it to heat it to the desired temperature, when it gets to this temperature the Bunsen is removed. I will use a thermometer to get exact temperatures. The temperatures I have chosen to use are: 0, 20, 30, 35, 40, 45, 50, 60, 80 and 100 degrees Celsius. Once the pieces of liver are at the desired temperatures then they are ready to be used to make the reaction that I will measure to get my results. Each piece of liver will be put into a separate test tube; each of these said test tubes would have an equal amount of hydrogen peroxide in them. I will be using 10ml of hydrogen peroxide per test tube for this experiment to keep it a fair test. When the liver pieces come into contact with the hydrogen peroxide a violent reaction will take place. Lots of frothy liquid will be produced and quite quickly rise up the sides of the test tube it is in. and will eventually stop. For the efficiency of each reaction to be measured I will measure how long it takes the frothy liquid to climb up the side of the test tube and flow over the top (if it does so). Each test tube has a volume of 50ml, which means that in the reaction, the hydrogen peroxide will have grown from 10ml to 50ml (including the gas in the reaction). The timing shall commence as the liver touches the hydrogen peroxide and stop the timing as the frothy liquid gains enough mass to reach the top of the test tube or stops getting any higher up the sides of the test tube. Once I have got all the results from the range of temperatures I have tested, I will do some of the temperatures again to show repetition has occurred and that the results were not a fluke or anomaly. Then with these newly acquired results, I shall build a table of results and some graphs to display what temperature the enzyme worked best at. I will not be able to get a precise reading but the answer should be inside a range of 5 degrees Celsius.
Safety: there are many safety aspects in the procedure of this experiment that I must consider before starting.
When cutting the liver I should be very careful with the blades that will be used, if my skin makes any contact with the liver or I bled then the skin should be washed immediately.
When using the water bath there are several things to be careful of. The Bunsen burner will be on a very hot setting so all clothing should be out of the way or tucked in so nothing will set alight. The hot water in the beaker should be treated with caution, as it will seriously burn the skin if it is spilt onto the skin. Safety goggles should also be worn so that if the water bubbles there is no chance of it popping up into my eyes and burning me.
When the reaction is taking place and starting it off I should keep my distance and have goggles on as the reaction will be very violent and could damage me.
In the process of tidying away the experiment I must be careful of objects such as the gauze and tripod as they will still be very hot and could burn me.
Fair Test: to keep the experiment fair, there are several things that need to be kept in consideration. Like: -
All the individual pieces of liver need to be the same size, which has been set as 1.1grams for this experiment. This is so that there will be an equal amount of catalase in each tube.
When heating the liver the temperature has to be kept constant and very accurate so that I can get the correct results and reactions.
I must use the same amount of hydrogen peroxide, which is 10ml, in each test tube so that there will not be larger or smaller reactions due to different amounts of hydrogen peroxide.
I need to be as accurate as possible with the timer to get the most accurate results for my results table.
Results
The table below shows the results gathered from the experiments. The first column shows the temperatures used, the second column shows the results in seconds from the first test, the third column shows the results from the second test in seconds and the fourth column shows the results from the third test in seconds.
Conclusion
Graph
The results on the graph are as follows, the vertical axis contains the times it takes for the reaction and on the horizontal axis are the temperatures that the liver was heated to.
The graph shows that the fastest reactions are all around the 40 degrees Celsius mark even thought the fastest reaction was at the temperature 35 degrees Celsius. The multiple results seem to correlate and show up no anomalies.
This graph shows the averages of the tests that had multiple tests done. It shows a very clear trend. It shows that the enzyme works, but not very well at the 0 - 20 degrees mark. At around 30 – 40 the results drop and the enzyme is at its most efficient. As the temperature rises the enzymes reaction time decreases more and more. By the time it gets to boiling point the enzyme is working very slowly indeed. This could be because it has been denatured or at least partly denatured.
Evaluation
Accuracy: The experiment went very well and all of the results gathered seemed to be accurate according to the trend that developed in the graphs. I was not able to do multiple tests at the 45-50 mark, the results I do have do fit but the average is not as accurate as I would have liked.
Improvement: the number one improvement I would make if I did the experiment again is to get more results to go towards a more accurate average graph. The readings could have been more accurate if better equipment was open to us like automated liver droppers and laser sensor timers. Overall though I am happy with my experiment as it managed to show a clear trend and the temperature that the enzyme worked best at.
Biology Sc1 Investigation