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Lab Report
At the top of the first page, place a title for your report with your
Lab Report
At the top of the first page, place a title for your report with your name immediately under the title. The title should be
specific to what will be described in your report including the specific tissue you used. Continue with your Introduction.
Introduction (approximately 10 sentences, organized into 2 or 3 paragraphs, which should follow the sequence of
questions given here). Why is catalase an important enzyme? What is the relationship between alcohol consumption and
catalase (two important points)? What organelle contains catalase and what subcellular fraction would we expect to
contain this organelle? How is catalase being measured in your exercise (i.e., will you follow loss of substrate or
appearance or product and very briefly how is that substrate or product being detected)? What are the two research-based
hypotheses that you will test in this exercise? In each case, how is the hypothesis being tested.
Methods. As in your previous report, you will cite my handout as the source of the methods used (one sentence) and
indicate only additions or changes that were made to the procedure (if any). Look back at the instructions to your Bradford
assay report if you do not remember how to word this citation of my handout.
Results. Remember that each table or figure must have a number and title and be accompanied by a brief legend. In
addition, there must be a paragraph-style presentation of your results. In this presentation of the results, you are guiding
the reader through each Table and Figure in sequence. It might make sense to have all of your “raw data” (the absorbance
values for each time point for each of the 4 fractions) in one table. For example, the first sentence of a paragraph of the
Results might read: “Absorbance (A500) values were determined every 15 seconds for 2 minutes for the P2C, S2C, P2E
and S2E fractions (Table 1).” Alternatively, you could present 4 Tables, one for each fraction. Either way, you should
continue by saying whether or not A500 values, which correspond to the product oxygen, increased with time as expected if
catalase was present in P2C. What about S2C? What about P2E and S2E? In any case, if A500 decreases or doesn’t
change with time, that indicates no catalase is present.
Figures 1 – 3. Regardless of whether you use one Table or more than one to start your results, you will display your
results in 3 Figures, each referred to as a “Time Course” because you have followed something over time. Each Figure
will have A500 on the vertical (y) axis and Time (min) on the horizontal (x) axis. Figure 1 will show two sets of data to
address hypothesis 1, P2C and S2C from the control tissues. For each data set generate a trendline (do not set the intercept
to force the line through the origin 0,0) and display the linear equation and R2 value for each timed series. Figure 2 will
display the results testing the second hypothesis and so will display the time courses for P2C and P2E (again, generate a
trendline, linear equation and R2 value for each timed series). This is repeating P2C which was already displayed in
Figure 1 but displays it for direct comparison to P2E. Use a third figure (Figure 3) to display the time courses for S2C and
S2E (again, generate a trendline, linear equation and R2 value for each timed series).
Your last Table. Extract the slope values from the linear equations in Figures 1-3 and display them in a Table. Ignoring
the repeats, you would have 4 slope values, one each for P2C, S2C, P2E and S2E. These slope values represent an initial
way of expressing enzyme activity because the change in A500/minute (the slope) is directly related to the change in
product [O2] per minute. Note: in any case where you are entering a slope of zero or a negative slope, do not complete the
remaining conversions since this is indicative of no catalase activity so enter 0 in the conversion column and in the
specific activity column. Otherwise, you are then going to convert each ΔA500/minute value to Δ[O2] /minute. You will do
this by applying the Lambert-Beer law and dividing each ΔA500/minute value by the extinction coefficient 0.01 to convert
it to enzyme activity (μmoles O2 per minute). Display these values in a new column. Lastly, to properly express these
enzyme activities they must be corrected for the amount of protein used. Go back to your Bradford assay results, extract
your concentration of protein for each fraction and calculate the amount of protein (mg) in 100 μl of the fraction. Note:
adjust to a different volume if we ended up using a volume other than 100 μl. Display this protein amount in another
column of the Table. Lastly, divide each value for μmoles O2 per minute by the corresponding amount of protein. Display
these results in the last column where the units will now be μmoles O2 per minute per mg protein (μmoles O2/minute/mg
protein). This is your final corrected activity known as the “specific activity” for catalase. You could use headings like
this to organize your Table:
Initial Slope Conversion to [O2] Protein Specific Activity
Sample ΔA500/minute μmoles O2 /minute mg μmoles O2/minute/mg protein
P2C
S2C
P2E
S2E
Discussion. Address each of the following in paragraph form.
First paragraph: address the quality of the data. A) In every case, did A500 increase with time as expected? Point out any
sample (if any) where this was not the case. B) All enzyme activities are based on the slope of the line generated for each
time sequence. Refer to your R2 values in assessing whether your data points fit a linear relationship in each case. i.e.,
was every time sequence linear? Note if there was any case where the R2 value was not acceptable (below 0.8) or
questionable (below 0.9). C) Based on your answers to these questions, how confident are you in drawing conclusions
using your catalase results?
Next paragraph: the first research-based hypothesis. Briefly restate the first hypothesis (this ties your discussion back to
your introduction). What do you conclude regarding your test of the hypothesis? Refer to specific numbers in your results
to support your conclusion. Remember that any negative slope or slope of zero is indicative of zero catalase activity:
oxygen would have to increase as a result of catalase activity.
Last paragraph: the second research-based hypothesis. Briefly restate the second hypothesis (again, this ties your
discussion back to your introduction). What do you conclude regarding your test of the hypothesis? Refer to specific
numbers in your results to support your conclusion. Again, remember that any negative slope or slope of zero is indicative
of zero catalase activity: oxygen would have to increase as a result of catalase activity
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