This is based on the fact that though an enzyme, being a catalyst, is not used up in a chemical reaction it can only bind with a maximum number of substrates, and convert these into H2O and O2.
The concentration of substrate will determine the speed of the reaction as it controls how many Hydrogen peroxide molecules are available to be converted by the enzymes and hence the production of O2. This gas is ultimately the telling measure of the rate of reaction as it controls the buoyancy of the paper sheet and hence how quickly it surfaces after sinking.
Variables
Materials
Method
- Collect materials.
- Crush Liver in the mortar and pestle until juice is present.
- Using the marker, indicate on one (1) test tube and one (1) beaker the concentration of 3% Hydrogen Peroxide.
- Fill the test tube with 25mL of Distilled water.
- Fill the beaker with 10mL of 3 % Hydrogen Peroxide.
- Using the pipette take a sample of the 3 % Hydrogen Peroxide and drop five (5) drops into the test tube.
- Lightly swirl the test tube to combine the two solutions.
- Using the tweezers, pick up one of the filter paper squares and immerse it in the crushed liver in the mortar and pestle.
- Using the second pair of tweezers remove any solid forms of liver from the filter paper.
- Place the catalase doused filter paper into the test tube.
-
On contact with the solution, begin the stop watch. The paper will slowly sink to the bottom, O2 bubbles will begin to form and lift the paper back to the surface
- Stop the timer when the paper reaches the top of the test tube.
- Record this time.
- Repeat steps 3- 13, replacing the 3% Hydrogen Peroxide with each of the other concentrations.
Data Collection
Results:
Figure 1 shows the time taken for each of the filter sheets to surface in seconds
Qualitative Results:
-
On contact with the solution, small O2 bubbles began to form on the surface of the Liver.
- These small bubbles collected around the sheet of filter paper
- The filter paper slowly begun to rise from the bottom of the beaker
- No other physical characteristics observed throughout reaction
Graphs:
Graph 1 shows the indirectly proportional relationship between time and concentration. Graphically represents 1 over the values in figure 1 .
Relationship: C is proportional to 1/T
Graph 2 shows the extended graph of the function which accurately models the data in graph 1 converted to a rate.
Data Processing:
Data Processing
Sample Calculation Average:
Mean(x) = Ʃ(x) (min) / (Number of x)
Where
Mean= the average value of the selected data
X= data values
Ʃ= the total sum of the data values
Number of x= the number of values in the x data series
e.g. Mean = (35 + 30 + 29) / 3
= 31seconds
Sample Calculation Rate of Reaction
Rate = 1 / Time
Rate (molecules of buoyancy/sec) = 1) / Time(sec)
Calculation [Whole Average]
Rate = 1/ 31
= 0.032258 molecules/sec
Figure 2 shows one divided by the time taken to surface so as to achieve a model of comparative rates
Conclusion
Statement
The rate or reaction between the Catalase and the hydrogen peroxide increase proportionally to the concentration of substrate. This continued until 8% was reached, at this point the rate was maintained. The greater the concentration of substrate the greater number of molecules was available to be converted into water and oxygen gas. Therefore the rate of reaction increased in the order of 3%, 4%, 6% and the fastest was 8%.
Explanation
The purpose of this investigation was achieved in the rate of action of the Catalase increased proportionally with the increase of substrate until the optimum reaction point was reached at which point the rate began to plateau. To account for error due to measuring falsities and equipment interaction the graph of concentration vs. rate was drawn. The rate of action was extrapolated using a log based trendline to compensate for the curving function. This extrapolation proved that a concentration of 8% H2O2 solute will reach the optimum rate of action of Catalase.
Graph 1 shows that in all cases the concentration increase resulted in a quicker surfacing time for the filter sheets doused in liver juices. If it is assumed that all sheets have equal numbers of Catalase molecules then it can be concluded that to reach the maximum rate of reaction a concentration of 8% of H2O2 molecules must be present in the system.
Evaluation:
Various assumptions were made when conducting this experiment, which are obvious when considering the large variation in results for the three trials. Clearly, since these results were significantly different extraneous variable alone cannot account for the entire discrepancies between values. There was a methodical error in making assumptions about concentration accuracies. It was false to presume that the concentrations marked on the bottles were entirely correct, as well that they had not been tampered with or through other courses been altered. The assumptions were rough approximations based on little evidence; hence they quite possibly are the reason for the slightly skewed results.
Also, when conducting the experiment considerations were not made as to the consistent quality of the liver/ Catalase. The condition of the liver was not monitored throughout the process which suggests that the enzymes may have been effect by temperature, humidity, and other outside variables. This could results in the denaturisation of the enzymes which would later be used in the experiment and would skew the results, altering the experiments controlled variable and ultimately providing false results.
In the future, to account for these errors, a mass spectrometer should be employed so test the exact concentrations of Hydrogen Peroxide, as well as the quality of the distilled water. More drops of substrate could have been added to provide a clearer result. Rather than a mortar and pestle being used to crush the liver, a blender would be more appropriate to ensure a better consistency and eliminate the effects of a changing enzyme concentration. Finally, the results should be duplicated in order to improve the quality of the mean results and to increase the R2 value of the graph.
