Catalase is an enzyme that is found in the liver. It is found extensively in mammalian tissues. It is present in the body to prevent the excess build up of hydrogen peroxide in the body. Hydrogen peroxide is created continuously by numerous metabolic reactions. In large quantities peroxide can be harmful to bodily tissues and so needs to be kept to an adequate level.
Apparatus
Bunsen Burner, 10x test tubes, tripod, gauze, heat-proof mat, beaker, water, stirring rod, thermometer, timer, 300cm3 of Hydrogen peroxide, measuring cylinder and 30 pieces of liver (each 1cm3).
Diagram
Method
1 The apparatus was set up as shown in the diagram.
2 The first test was prepared at the right temperature (20°C) and the first piece of liver was placed into the test tube.
3 The stirring rod will be used to hold the liver in the test tube as the reaction is timed.
4 When the reaction has stopped the time displayed on the timer will be recorded into a results table.
5 The next test tube of Hydrogen peroxide will be heated to the desired temperature between 20°C and 90°C and steps 2 – 4 will be repeated.
6 This whole process (steps 2 – 5) will be repeated three times in order to obtain a more accurate set of results.
Fair Test
- Only the temperature of the Hydrogen peroxide will change throughout the investigation.
- The amount of Hydrogen peroxide in each test tube will be the same.
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The amount of liver placed into the test tubes will be the same size (1cm3).
Safety
During the investigation whilst heating the Hydrogen peroxide the whole group will be standing up and wearing safety glasses.
Results
Analysis
Having drawn a graph and considered my results I can see that the Hydrogen peroxide appears to form a straight-line pattern. This shows that as the temperature rises, the rate of reaction rises as well. However, most of my results follow this pattern but there are several that appear to be anomalous. The first set of results I gathered are completely different to the second set of results I gathered but the general trend is that the time eventually decreases, by quite a margin, as the temperature increases. Perhaps my prediction was wrong and the enzyme, catalase, increases its efficiency as the temperature increases and does not work best at 37°C This may suggest an unstable solution was used. I know that hydrogen peroxide denatures very quickly. The reaction time appears to decrease as the temperature rises. This is visible in both of the sets of results that I have gathered.
Conclusion
I was expecting the catalase to react best with the hydrogen peroxide at around 37°C but this does not seem to be the case. The reaction times seem to be linear. The reaction time decreases accordingly with the increase in temperature. If this is true then my prediction was wrong. I have reason to believe however that most of my results are anomalous.
Evaluation
It is my opinion that the investigation that I have carried out into the affect of liver catalase with hydrogen peroxide was in fact not a success. I believe that the results I have gathered maybe completely anomalous. This could be due to the rapid denaturing of the hydrogen peroxide in the air or through inaccurate timing and observations.
To prevent inaccurate results if I were to carry out the investigation again I would use a more accurate timing method such as a digital timer. An analogue watch is not accurate enough method of timing to gather effective results. I would also consider when the reaction starts and finishes and then stick to that assumption. During the investigation the observations I carried out were not accurate. I can tell this by looking at my graph; the results do not run smoothly, there are two results that are a long way from the line of best fit that suggests that these two results have to be anomalous. It was difficult to tell exactly when a reaction had stopped as bubbles were constantly being produced by the hydrogen peroxides denaturing.
