Appendix Lab Report. Guidelines on report writing PDF

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Tells the proper way how to write a lab repot and proper formatting including significant figures, graphs and tables....

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APPENDIX A: Lab Report Guidelines SECTION I: INTRODUCTION WHAT IS IT? Think of the introduction as an inverted triangle that starts with broad strokes and narrows to focus on your experiment. Present general background information, then introduce relevant observations and questions. Finish with your specific hypotheses and a prediction. WHAT TO DO State the question(s) to be answered and explain both what the experiment sets out to do and how you will interpret the results. Be concise and clearly communicate the purpose of the experiment to the reader. THINGS TO REMEMBER •

Be brief but include definitions of any unfamiliar terminology

•

Include citations for all facts and thoughts that are not your own (e.g. textbook, lab manual)

SAMPLE INTRODUCTION AND CRITIQUE 1 This study focuses on enzymes and what makes them work. Enzymes are an important part of every living organism 1. Enzymes are involved in the digestion processes in the human body2. The object of this experiment is to get the substrate, catechol, to the product, benzoquinone, by way of the enzyme, catecholase. Experiment one alters the amount of enzyme to prove that the more enzyme you have, the faster the reaction takes place 3. Experiment two adds ascorbic acid to lower the pH. The goal of this is to prove that increased acidity stops a reaction4,5. 1. Enzymes are referred to as an "important part of every living organism." This is a poor definition, since it fails to provide a basis for understanding later terminology e.g. substrate. 2. This sentence does not belong in this report because the experiment does not involve a digestive enzyme. All information included in the introduction should be relevant. 3. This sentence explains what was done but fails to state the purpose of the experiment. The rationale for altering enzyme concentration was to observe effects on the reaction rate. 4. It is inappropriate to assume that the results will “prove” anything about enzymes. The goal of a scientific experiment is to collect data that will either support or falsify a hypothesis. 5. No outside sources are cited. Including references establishes that the information presented is credible, and directs the reader to a source of additional reading on the topic.

SAMPLE INTRODUCTION AND CRITIQUE 2 Enzymes are catalytic proteins that accelerate reactions by lowering the activation energy (Campbell, 1996). An enzyme is specific in the reactions in which it takes part; it contains an active site that allows only certain reactants, called substrates, to bind to it1 (Campbell, 1996). The first experiment examined how the rate of reaction of catechol and oxygen to form benzoquinone changed while the concentration of the enzyme catecholase was varied2. It was hypothesized that enzyme concentration affects reaction rate, and predicted that reactions with greater concentrations of enzyme would yield a greater net conversion of substrates to product. In order to function, an enzyme must retain the unique shape of its active site (Campbell, 1996). Environmental factors such as ion concentration and pH have been shown to alter the conformation of an enzyme’s active site3. The second experiment examined changes in the rate of reaction of catechol and oxygen as the pH was varied 4. Reactions run at a neutral pH were expected to convert more substrate than reactions run in an acidic environment (pH 4.0). 1. The author clearly defines terminology relevant to the experiment. “Enzyme” is defined concisely yet in enough detail for the reader to understand the purpose of the experiment. 2. This is a concise statement of the question that the first experiment attempts to answer. It is specific and demonstrates a clear understanding of the purpose of the experiment. 3. An explanation of the relationship between protein shape and active site function is important to understand how pH may affect enzyme activity. The level of detail needed in an introduction will vary; terms that require definition in introductory biology may be assumed in advanced courses. If in doubt, ask your TA what information is appropriate. 4. This is another good example of stating the purpose of the experiment. It is specific, and notes that the expected result of varying pH would be a change in reaction rate. ____________________________________________________________________________

SECTION II: METHODS WHAT IS IT? This section provides the reader with all relevant details about the experimental procedure, and serves as the basis by which other scientists might replicate the experiment. WHAT TO DO This section requires you to trace the experimental logic step by step, establishing a strong understanding of the process. The most challenging aspect of this section is determining the appropriate level of detail. Students new to scientific writing often include extraneous information. Be concise, yet informative; include only information necessary for the reader to develop an adequate understanding of the experiment and to recreate it if they so choose. THINGS TO REMEMBER 

Do not simply list the materials used; introduce each at the most relevant step in the process



Write in past tense and use first or third person as appropriate to the discipline

SAMPLE METHODS AND CRITIQUE 1 To prepare a catecholase extract, a potato was skinned and diced. 30 g potato and 150 ml distilled water were pureed in a blender for two minutes. The resulting solution was filtered through four layers of cheesecloth and stored in a clean, sealed container. Four labeled test tubes were prepared with different amounts (see Table 1) of the following reagents: buffer (pH 7), 0.1% catechol substrate, and distilled water1. The wavelength of the Spectronic 20 was set to 540 nm. A blank was prepared with no catechol substrate (tube 1) and used to calibrate the spectrophotometer to zero absorbance2. The extract to be tested was added to each tube immediately before reading the absorbance. 1.0 ml catecholase extract was pipetted into tube 2, and it was inverted and placed in the spectrophotometer. The absorbance was read and recorded at time zero (t = 0) and each minute until ten minutes had elapsed (t = 10). The same protocol was used to take absorbance measurements for tubes 3 and 4. 1. This procedure is described in a way that can be clearly understood, without excess detail. 2. Calibration is a small but important detail that is required for a reader to repeat the experiment. Keep this in mind when deciding what to include in this section.

SAMPLE METHODS AND CRITIQUE 2 A potato and knife were obtained for this experiment. Distilled water, a blender, cheesecloth, a container with a lid, and eight test tubes were also used. A Spectronic 20 spectrophotometer was used for the experiment, as were buffers of pH 4, 6, 7, and 8. Catechol substrate, Parafilm covers, KimWipes, and pipettes were also used, along with a pencil and pad to record results3. 3. This simple list of materials is not useful. The Methods section should mention the materials and equipment used, but should do so in context of the experimental procedure.

SAMPLE METHODS AND CRITIQUE 3 In preparing the catecholase extract, a potato was skinned and diced. A balance was used to obtain 30 g of the diced potato. 150 ml of distilled water was poured into a beaker, then added to the potato. The cover of a kitchen blender was removed, and the potato and water added to the blender. The cover was placed on the blender and the power button was depressed. The power button was pushed again to stop the blender 4. The resulting solution was filtered through four layers of cheesecloth. The extract was stored in a clean, sealed container. 4. This is extraneous detail not necessary to explain or repeat the procedure. Any reader can presumably turn a blender on and off without being told that a button was pushed.

SECTION III: RESULTS WHAT IS IT? This section must present experimental data to the reader in a logical, orderly manner. It is critical to include all data that was used in drawing any conclusions presented in the Discussion. WHAT TO DO Write the Results immediately after writing the Methods section. The natural progression should help you present your findings in a clear, consistent way. This section includes tables and/or graphs of the data, each of which must be accompanied by a title and legend. A brief text section is required to clearly recapitulate the information presented in these figures. THINGS TO REMEMBER Organize your data in a logical way so that a reader can follow your thought process and the flow of the experiment. As you introduce the data you may point out trends or patterns, but do not interpret it; all interpretation belongs in the Discussion. Remember that the word data is plural (singular = datum) and be attentive to subject-verb agreement (e.g. the data are). SAMPLE RESULTS AND CRITIQUE 1 Protein Values Experiment Vehicle Vehicle/LPS Drug Drug/LPS

Absorbance 0.61 .66 0.69 0.61

Protein 2.2 2.36 2.50 2.22

This table gives the reader incomplete information. It has no title, just a poorly descriptive label. There is no explanation of what “Protein Values” were measured and under what conditions, and measurement units are missing from the column labels. Absorbance values mean nothing if the reader doesn't know the wavelength at which they were read.

SAMPLE RESULTS AND CRITIQUE 2 Table 1: Absorbance Readings and Corresponding Protein Concentration Values Experimental Group Vehicle Vehicle/LPS Drug Drug/LPS

Absorbance (595 nm) 0.61 0.66 0.69 0.61

Protein Concentration ( g/l) 2.20 2.36 2.50 2.22

Table 1 demonstrates that the concentration of protein found in each sample is similar. This table has an appropriate and descriptive title, and all columns include appropriate units of measurement. It is also followed by a brief legend describing the data.

SAMPLE RESULTS AND CRITIQUE 3 Figure 1: Reaction rates and time

This graph is missing axis labels with measurement units, and there is no indication of which experimental group each curve represents. It is not accompanied by a text legend, and trends are not identified.

SAMPLE RESULTS AND CRITIQUE 4

Tube 2

ABSORBANCE (595 nm)

Tube 3

Tube 4

TIME (seconds)

Figure 1: Absorbance as a function of reaction time. Values represent the rate of conversion of catechol to benzoquinone. At low pH (tube 2) we see a slight dropoff before a return to the initial rate. The control (tube 3) shows a gradual increase before leveling off at 7 seconds. At high enzyme concentration (tube 4) we see a slight increase in the first 3 seconds.

The axes and data are appropriately labeled. The graph is also accompanied by a descriptive legend pointing out specific trends in each curve.

SECTION IV: DISCUSSION WHAT IS IT? In this section, briefly restate the hypothesis and explain why the predicted results were expected. Then interpret the data, and conclude whether they support or falsify the hypothesis. Think of the Discussion as upright triangle ▲. It begins narrowly with an interpretation of your specific data set, and broadens to relate the data back to the larger question at hand. WHAT TO DO Write the discussion directly after the results. Compare how the actual results relate to those predicted, and state whether or not your hypothesis was supported and why. Describe any deviations from the experimental procedure as outlined in the Methods section. If the results are unexpected, consider the integrity of the experimental design. What could be changed to improve it? Also discuss any future experiments you could conduct to further explore your topic.

SAMPLE DISCUSSION AND CRITIQUE 1 The results of the first experiment support the hypothesis that the rate of substrate conversion increases with increased enzyme concentration1. Tube 2 had the highest concentration of catecholase, and also had the highest absorbance values. Since absorbance is a measure of reaction rate, the greatest rate of conversion of catechol and oxygen to benzoquinone was seen in Tube 22. In these conditions, the absorbance increased rapidly before leveling off (Figure 1). Tubes with lower concentrations of enzyme had lower rates of conversion, as expected. However, an unexpected result was also seen in Tube 2; between 6-8 minutes, a decrease in absorbance was observed. One possible explanation is that the substrate settled to the bottom of the tube, making it less accessible to the enzyme and preventing it from acting efficiently 3. Inversion of the tube to mix its contents led to a further increase in absorbance. Future experiments that involve constant mixing could be run to test this possibility. The folding of polypeptide chains forms the specific three-dimensional shape of an enzyme. This shape is critical for enzyme activity; environmental conditions that affect enzyme shape also affect efficiency. Each enzyme operates most effectively in an optimal pH range, typically pH 6-8. Levels outside this range can denature the enzyme and impair its catalytic activity. Our results support this hypothesis for catecholase. Tubes 3 and 4 had similar absorbance values, and therefore similar enzyme activity. However, at pH 4 in tube 2, lower activity was observed. This is likely due to the fact that the highly acidic environment denatured the enzyme.

1. The author starts by summarizing the data, then moves into interpretation. The first sentence states both what was expected and whether the data support the hypothesis. 2. A good discussion includes both well-reasoned ideas and detailed support of these ideas. The author effectively explains why the experimental results support the hypothesis. 3. The author discusses an unexpected result and a possible cause; this shows that problems with the experiment were thoughtfully considered. The author does not accept blame; instead, he considers the methods used, then presents and justifies a possible explanation.

SAMPLE DISCUSSION AND CRITIQUE 2 Enzymes catalyze reactions by lowering the activation energy of the reaction1. Catecholase, an enzyme found in potatoes, converts catechol to benzoquinone in the presence of oxygen. It is expected that more benzoquinone will be formed in the presence of a higher concentration of catecholase. This hypothesis was supported by the results obtained. Tube 2 contained the highest level of enzyme and exhibited the highest absorbance, which means that the most product was formed in this tube. Tube 4 had the lowest level of enzyme and displayed the lowest absorbance. Any unexpected results were likely due to human error; absorbance may have been read incorrectly2. Enzymes are affected by environmental factors such as pH 3. The rate at which an enzyme forms product depends on how close the environment is to its optimum. In the second experiment, the pH of the medium was varied. The general trend seen was that the more acid that was added to the tubes, the less product was formed. The more acidic solution caused the enzyme to work less efficiently.

1. The first two sentences belong in the Introduction. The expectations are clearly stated, as well as whether they were supported by the data; however, this section lacks specific detail. 2. The author fails to provide a logical explanation for unexpected results. He blames himself, and passes off the result as a consequence of human error. 3. The argument for the effect of environmental factors on enzyme activity is poorly developed. It should explain that acidity causes enzymes to denature, thus reducing their efficiency. ____________________________________________________________________________

ACKNOWLEDGING SOURCES A lab report should include a reference section listing each source you consulted while writing the report. Each source should also be acknowledged in the text of the report where relevant. You may use any acceptable format as long as you are consistent. Examples of how to cite different types of references are given below: Website: Nation League of Omnology, www.NLOO.org/home/ include URL and organization Journal article: Storm, I.C. 1994. Omnology at the crossroads. J. Omnol. 22:1–44. Book: Calm, M. 1994. Omnology has passed its peak. University of Chicago Press, Chicago. Article in a book: Storm, I.C. 1994. Whither goest omnology? pp.33–44 in M. Calm, ed. The future of omnology. University of Chicago Press, Chicago.

References Pechenick, J.A.,1993. A Short Guide to Writing About Biology, Tufts University; Harper Collins College Publishers. Excerpts were adapted from lab reports by Richmond University students Beth Brandler. Molly Cage, Daniel Hocutt, Bruce Ingersoll, Jeffrey Lewandowski, and Jonathan Wakefield....