How to Write a Lab Report
What is a Lab Report?
A scientific lab report is simply a paper that explains to an audience an experiment that was done in order to support a hypothesis or null-hypothesis.
Lab reports are common in the scientific community and can become published in accredited scientific journals after peer review. Lab reports can also be written for college classes, as well as other professional areas including engineering and computer sciences.
Here is an example of a lab report that was actually submitted and received a perfect grade along with step-by-step instructions on writing an effective lab report.
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Main Parts of A Lab Report
The main parts of a lab report are summarized below. Generally, the format does not vary much. A lab report typically includes all of the following sections in the same order. Sometimes acknowledgments are skipped in less formal reports that are written for a college class. In addition, the introduction and abstract are sometimes merged into one section in a college setting.
- Materials and Methods
Below, the top text gives instructions for what you should be focusing on in that section and the bottom gives an example.
Design a title that is not too vague and not so specific that you end up writing a 3 sentence title. A bad, vague, example would be "Influence of various factors on amylase activity". A good setup is shown below
Influence of pH, temperature, and concentration on amylase activity
(by: Author's Name)
Writing the abstract is pretty easy, there is an introduction sentence, then explain what you did in the experiment in the next few sentences (1-2) and conclude with your results (2-3 sentences). Remember to use a past-tense and passive voice throughout the entire lab report. Do not write "We, our, my, ours, I..." etc.
Many animals use amylase, an enzyme found in the saliva, to digest starch to maltose and glucose. The effect of concentration, pH, and temperature on amylase activity was examined to determine how these factors affect enzyme activity. Activity was measured by measuring the rate of disappearance of starch using I2KI, a color changing indicator that becomes purple in the presence of starch. The results suggest that as concentration of amylase decreases, the rate of starch digestion decreases. Similarly with pH, as it deviates away from 6.8, the rate of starch digestion decreases. Finally, the rate of starch digestion decreases as it deviates from the ideal body temperature of 37°C. Overall, the results suggest that enzyme activity may be affected by factors such as concentration, pH, and temperature.
The introductions is a longer version of the abstract without the "methods" or "results" part. Essentially you are introducing a reader to your topic and it's background. You are also writing a hypothesis and telling your reader what that hypothesis is. So remember, introduction has two important parts:
- Background on topic
Figures: If you reference figures or tables in your report, you can choose to integrate them as you go, or put them all at the end of your lab report attached as a separate paper after the references section. It makes formatting easier.
The kinetics of a reaction, its rate, is usually established by measuring the amount of substrate consumed or the amount of products formed as a function of time. An assay is usually performed to determine this type of information. The rate of a reaction depends on more factors than the three examined. In addition to temperature, pH, and concentration other factors such as the structure of the substrate, the amount of concentration of the substrate, the ionic strength of the solution, and the presence of other molecules that can act as activators or inhibitors1.For the factors that were examined it was predicted that as amylase concentration decreases the enzyme function decreases as measured by the rate of starch digestion. For pH it was predicted that as it deviates from 6.8, the ideal pH for amylase to function, the activity of the enzyme decreases. Lastly, for temperature it was predicted that as the temperature fluctuates away from 37°C either higher or lower, amylase activity will also decrease. The effect of concentration, pH, and temperature on amylase were examined to determine how these factors affect enzyme activity. The importance of enzyme inhibition was studied in an experiment in which Inhibition of starch digestion by alpha-amylase inhibitor reduced the efficiency of utilization of dietary proteins and lipids and slowed the growth of rats. The study saw that at the two highest levels of amylase-inhibitor 3.3 and 6.6 g/kg diet, the growth rate of rats and apparent digestibility and utilization of starch and protein, was significantly less than in control rats2. The mechanisms for starch digestion of amylase depend on the class of the amylase enzyme. There are four groups of starch-converting enzymes: (i) endoamylases; (ii) exoamylases; (iii) debranching enzymes; and (iv) transferases. Endoamylases cleave the α,1-4 glycosidic bonds present in the inner part of the amylose or amylopectin chain. Exoamylases either cleave the α,1-4 glycosidic bonds such as β-amylase or cleave both α,1-4 and α,1-6 glycosidic bonds like amyloglucosidase or glucoamylase. Debranching enzymes such as isoamylase exclusively hydrolyze α,1-6 glycosidic bonds. Transferases cleave an α,1-4 glycosidic bond of the donor molecule and transfer part of the donor to a glycosidic acceptor while forming a new glycosidic bond between glucoses3. Figure 1 summarizes the different methods of cleavage. Regardless of the method of cleavage, all of the classes of amylase enzymes can be affected by concentration, pH, and temperature.
Materials and Methods
In this section of the lab report you are ONLY stating your materials and methods. Do not explain results or discuss them here.
The methods section can be written as separate paragraphs for each different experimental set up you had to perform or can be split off into subsections each with its own subtitle.
Concentration Experiment Setup
Five serial dilutions of amylase were created, ½, ¼, 1/8, 1/16, and 1/32. The ½ dilution was set up using 4 ml of diH2O and 4 ml 1% amylase solution. Four ml were transferred over to make the ¼ dilution and so on with each dilution. 2 ml of each dilution was added to tubes containing 2 ml of pH 6.8 buffer solution. 24 well plates were prepared with 500 ul of I2KI. One ml of a 1% starch solution was added to the tubes prior to the start of each timed experiment and considered T0. 300-500 ul of the dilution mix was added to the 24 well plates every 10 seconds until the solution no longer turned purple/all starch was digested or until the sample ran out. This was repeated for all 5 tubes and the respective times were recorded.
pH Experimental Setup
Six test tubes at different pH’s (4, 5, 6, 7, 8 and 9) were prepared by adding 5 ml of each pH buffer solution to 1.5 ml of 1% amylase solution. Twenty-four well plates were prepared with 500 ul of I2KI. One ml of a 1% starch solution was added to the tubes prior to the start of each timed experiment and considered T0. 300-500 ul of the dilution mix was added to the 24 well plates every 10 seconds until the solution no longer turned purple/all starch was digested or until the sample ran out. This was repeated for all 6 tubes and the respective times were recorded.
Temperature Experimental Setup
Four test tubes were prepared by adding 2 ml of 1% starch solution, 4 ml diH2O, 1 ml, and 6.8 pH buffer solution and were then placed in water-baths at 80°C, 37°C, 22°C, and 4°C for 10 minutes. Four separate tubes with 1 ml of 1% amylase solution were also incubated at those temperatures for 10 minutes. 24 well plates were prepared with 500 ul of I2KI. While keeping the tubes in their respective water-baths to maintain a constant temperature 1 ml of the heated/cooled 1% amylase solution was added to the tubes prior to the start of each timed experiment and considered T0. 300-500 ul of the dilution mix was added to the 24 well plates every 10 seconds until the solution no longer turned purple/all starch was digested or until the sample ran out. This was repeated for all 4 tubes and the respective times were recorded.
Lab Report Results
Writing the results section in a lab report is as easy as writing the methods. Here you are simply stating what your results were and that's it. Do not discuss results here, just state them. Again, use subheadings if it is appropriate for your experiment, in this case, it is.
Amylase Activity at Various Concentrations
Two trials were performed for this part of the experiment. In the first trial (figure 2) the activity of amylase (as measured by time taken to fully digest starch) had no logical correlation as the serial dilutions decreased in concentration of amylase. The second trial (figure 3) had an almost linear pattern with the ½ dilution being 10 seconds faster than the ¼, 1/8, and 1/16 dilutions and 40 seconds faster than the 1/32 dilution.
Amylase Activity at Various pHs
The activity of amylase (as measured by time taken to fully digest starch) was tested at pHs of 4, 5, 6, 7, 8, and 9 as seen in figure 4. The time taken to digest starch (in seconds) was 50, 50, 20, 10, 20, and 20 respectively. As the pH increases toward the ideal pH for enzyme activity of 6.8 the time taken for complete starch digestion decreases to about 10 seconds.
Amylase Activity at Various Temperatures
The activity of amylase (as measured by time taken to fully digest starch) was tested at four different temperatures of 80°C, 37°C, 22°C, and 4°C as seen in figure 5. The time taken to digest starch (in seconds) was 170, 100, 170, and 100 respectively. The trial for 22°C was repeated a second time when the first trial gave a time of 20 seconds.
The last major part of writing a lab report is the discussion. This should be the longest section and...
- Explain what the results mean
- Discuss if they support the hypothesis or not
- Explain possible sources of error
- Discuss further experimentation that can be done
In the concentration experiment of amylase it was expected that as the concentration of amylase is decreased, it should take longer for the digestion of starch to be completed and therefore less time until the I2KI indicator turns yellow. The results shown did not reflect this hypothesis. There was no logical correlation between time and starch digestion as the serial dilutions decreased in concentration of amylase. In the first trial the highest concentration of amylase actually took longer than the lowest concentration of amylase to digest the starch. The 1/16 dilution digested starch the fastest. With these results having no clear explanation, a second trial was set up using a fresh batch of I2KI, new amylase enzyme, and a new starch solution. In the second trial the ½ dilution took 10 seconds less than the ¼, 1/8, and 1/16 dilutions to digest starch and 30 seconds less than the 1/32 dilution. This was a more appropriate result since it was expected that a higher enzyme concentration would react faster than a sample with barely any enzyme or none at all. However, in all cases the sample ran out before the I2KI could start turning yellow. This could be due to the fact that 24 well plates were used instead of 48 well plates, and thus more sample had to be added to see a color change. In the first trial however, a possible reason for the illogical results could be the preparation of any of the solutions that were used in the reaction including the starch precipitating out of solution before if had a chance to be mixed with the enzyme and the rest of the reactants.
Activity of amylase was also measured at different pHs. It is known that amylase functions optimally at a pH of 6.8, therefore 5 different pHs above and below 6.8 were tested: 4, 5, 6 ,7 and 8. The results in figure 4 show that as a pH of 6-7 was approached the time required for starch to be digested and I2KI to turn yellow was down to 20 and 10 seconds respectively. As we deviated from the ideal pH the time required went up. This second experiment functioned as predicted despite using the same reaction mixes as in trial one of the concentration experiment leaving a possibility that the error in the first trial might have been in the way the dilutions were set up, (incorrect pipetting). The results of the pH experiment were expected since changes in pH can affect the shape of an enzyme and alter the shape or charge properties of the substrate so that either the substrate does not bind to the active site or the enzyme cannot bind to it.
An enzyme can also be denatured by temperature, therefore the activity of amylase was tested at four different temperatures of 80°C, 37°C, 22°C, and 4°C as seen in figure 5. Since amylase is an enzyme found in animal saliva, it functions optimally at body temperature, 37°C so it was expected that at 37°C the time it takes for starch digestion will be lowest. The time taken to digest starch (in seconds) was 170, 100, 170, and 100 respectively. One possible reason for seeing a time of 100 seconds at both 37°C and 4°C was that instead of keeping the reaction tubes in the water-baths or ice baths as the experiment was being performed, they were taken out and left to sit before the experiment started, possibly giving the enzyme a chance to re-nature. The other two results for 80°C and 22°C both are indicative that amylase functions less optimally at a temperature other than 37°C. These results indicate that temperature does have an effect on amylase’s ability to digest starch. At 80°C much of the enzyme could have been denatured explaining the extra 70 seconds it took from the ideal 100 seconds at 37°C. At 22°C it still is possible that the reaction might not be so kinetically favorable which explains why the reaction still happens, but 70 seconds slower than at 37°C. The difference in times might have been even greater if the lab protocol was followed where it called for time measurements every 30 seconds. Instead time measurements were taken every 10 seconds as in the first two experiments.
Future experiments could focus on comparing the different modes of inhibition for different classes of amylases as mentioned in figure 1. Since every class functions to cleave starch in a slightly different way, two different classes can be compared to each other using the above three experiments to test which class of amylase retains more activity when subject to the three different constraints of concentration, pH, and temperature.
Citing references in a lab report can be done in a few styles, most commonly used is the ACS (American Chemical Society) style of citing for chemistry and CSE (Council of Science Editors) for biology.
- BMB443W- Laboratory in Protein Purification and Enzymology – Lab Manual
- Pusztai A, Grant G, Duguid T, Brown DS, Peumans WJ, Va Damme EJ, Bardocz S. 1995. Inhibition of starch digestion by alpha-amylase inhibitor reduces the efficiency of utilization of dietary proteins and lipids and retards the growth of rats. Journal of Nutrition 125(6): 1554-1562.
- Marc JEC van der Maarel, Bart van der Veen, Uitdehaag JCM, Leemhuis H, Dijkhuizen L. 2002. Properties and applications of starch-converting enzymes of the α-amylase family. Journal of Biotechnology 94(2): 137-155
As mentioned earlier, figures can be incorporated into the body of the lab report as you reference them in text, or they can be added at the end of a lab report separately to help with formatting issues that could occur if they were cited in-text.
Make sure to explain all figures below them, and if you have a table, the explanation always goes before the table.
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- How To Write A Proposal Essay/Paper
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