Effects of temperature and enzyme concentration on enzyme activity.

Writing the Laboratory Report

Deadline: Monday 20th February

Writing style

The report will be reviewed for content, interpretation of data and how well you express yourself in scientific writing.
The text should be arranged into logical paragraphs and sentences.

Each paragraph should start with a subject sentence that introduces the information in that paragraph.

Proof read your work several times to make sure that all the information is correct; it is logically presented and clear.

When you write the methods and results Sections use past tense because you have completed the experiments by the time you begin writing the report.

Scientific writing should be clear and concise. Don’t use five words when two will do.

Too long: Enzymes are proteins which break down bonds holding large nutrient molecules into smaller forms for cells to be able to digest Better: Enzymes are biological catalysts.

This should be informative
Very long
E.g. Investigating the effect on enzyme activity and the rate of reaction, when enzymes are exposed to different temperatures and enzyme concentrations Informative and specific
E.g. The effect of temperature and enzyme concentration on the activity of Chymosin.

This section is an overall summary of the report. Hence, it should include a sentence or two on the rational for the work. A brief description of the method(s) used. It should contain the main findings from the investigation.

It should NOT contain any discussion of your findings. However, you must include the conclusions that you can draw from the study.

The first part of the introduction should set the framework for your experiment by briefly providing background information. You should present information that is related to the topic.

Ensure that you give proper citations when you state facts or ideas from reference sources.

In the last part of the introduction you should describe the specific questions that you studied. State what you did in a general way, e.g., “We investigated the effect of factors affecting the rate of milk curdling in the presence of cymosin”, but do not give specific details of your Methods or Results.

METHODS (The method and procedures must be done in past tense sentences and not 1st person)
The experiment will have been done by the time you write your report, so use past tense. The method section includes a brief outline of the procedures used in the experiments.

The purpose of this section is to allow other scientists to duplicate the methodsyou used. Hence, it should be detailed enough so that someone else can read your report and repeat the experiment.

However, you should NOT include trivial details such as “we used test tubes that were 10 cm long,” or “the enzyme was kept in a beaker before the experiment began.”

Example 1:
The appearance of iodine provided was noted. Ethanol (5 mL) was transferred to a test tube and the colour and temperature of the solvent was recorded. The solvent was added to the tube containing iodine and the temperature change was monitored whilst stirring with a thermometer.

Example 2:
A test tube of iodine was mixed with ethanol. The colour and smell was noted in our lab book. The iodine was completely dissolved using a thermometer. The temperature was recorded in the lab book. Which example is better and why?
(Procedures for practical experiment)

Procedure i
1. Measure 5 mL of milk into each of the 12 test tubes.
2. Place 3 prepared test tubes in the 37°C water bath.
3. Place 1 prepared test tube in the 0°C ice bath.
4. Place 1 prepared test tube in the 50°C water bath.
5. Place 1 prepared test tube in the 80°C water bath.
6. Leave the remaining 6 tubes in the test tube rack until the milk within them reaches room temperature (check this and note it).

Procedure ii. Effect of enzyme concentration on rate of reaction at room temperature experiment
1. Number the 6 tubes remaining at room temperature from 0 to 5.
2. Using a Pasteur pipette quickly add one drop of neat chymosin to tube 1, two drops to tube 2 and so on until tube 5 “ do not add any chymosin to the control tube 0.
3. Immediately swirl all the tubes and start the timer.
4. Observe all 6 tubes at regular intervals for signs of the milk curdling. Record the times at which each milk sample is completely curdled.

Procedure iii Effect of enzyme concentration on rate of reaction at 37°C experiment
1. Number the 3 tubes in the 37°C water bath from 6 to 8. (Microbial rennin (chymosin) is the same enzyme as that purified from rennet, but is extracted from microbes. Thus, no calves were harmed during the making of this practical. )
2. Using a Pasteur pipette quickly add one drop of 1/10 diluted chymosin to tube 6, two drops of diluted chymosin to tube 7 and one drop of neat chymosin to tube 8.
3. Immediately swirl all the tubes and start the timer.
4. Minimise the time the tubes are removed from the water bath to avoid the milk cooling down and work quickly, curdling might happen much faster than in Experiment 1.

Procedure iv. Effect of temperature on enzyme activity experiment
1. Add one drop of neat chymosin to the three tubes in the 0°C (tube 9), 50°C (tube 10) and 80°C baths (tube 11).
2. Immediately swirl all the tubes and start the timer.
3. Minimise the time the tubes are removed from the water bath to avoid the milk cooling down and work quickly.
If no curdling is observed in some of the tubes during the time of the lab note: no curdling observed in tube X after Y minutes.

The results section should always starts with normal paragraph (text ) format, NOT with tables or figures. You MUST first draw the reader’s attention to EACH table and figure before they appear, indicate what they show, and
summarize the important data in each. Good Example of How to Begin the Results:

e.g. Table 1 shows the results obtained for conductivity of solutions of aqueous sodium chloride and water samples from different sources. A plot (Figure 1) of concentration of standard solutions of sodium chloride as a function of conductivity shows a linear relationship with a regression coefficient of 0.9988.
As with all writing the results should be organized into coherent logically organized paragraphs and sentences.
Figure: a graph, picture, or diagram
A figure will have a detailed legend at the bottom
Table: something that contains only numbers, and has a detailed legend at the top. The units for each column of data should be in the column heading and not throughout the column
Report ALL data, even if it was unexpected. Types of data will include:
General observations made during the experiments
Quantitative results (summarized as means, standard deviations etc.), which normally appear in figures and/or tables
The results of statistical analyses. This can be done in the text if it is simple. If there are many numbers, put the data in a table.

Class results
No. drops of chymosin 0 1 2 3 4 5 1 drop 1/10 2 drops 1/10 1 1 1 1
Temperature Room Room Room Room Room Room 37 C 37 C 37 C 0 C 50 C 80 C
Time taken for 5 mL of milk to coagulate / seconds
Group 1 Nothing nothing 2160 2091 1982 1740 863 293 153 nothing 41 nothing
Group 2 Nothing Nothing 2165 2100 1958 1826 1126 779 300 Nothing 42 Nothing
Group 3 Nothing 3320 2910 2460 2430 2400 930 460 375 Nothing 50 Nothing
Group 4 Nothing Nothing Nothing Nothing Nothing Nothing 834 390 60 Nothing 100 Nothing
Group 5 Nothing Nothing 3420 3780 3630 3512 1440 2100 240 Nothing 70 Nothing
Group 6 Nothing 3529 3335 2435 2145 1745 930 565 250 Nothing 90 Nothing
Group 7 Nothing Nothing Nothing 3420 3410 3050 635 440 440 Nothing 120 Nothing
Group 8 Nothing 3180 2760 2364 2051 1925 1842 632 550 Nothing 54 Nothing
Group 9 Nothing Nothing 3520 3128 3024 2559 772 581 171 Nothing 16 Nothing
Group 10 Nothing Nothing Nothing 2400 2200 2040 600 780 120 Nothing 85 Nothing
Group 11 Nothing 3287 3420 2990 2700 2680 530 1935 530 Nothing 28 Nothing
Group 12 Nothing Nothing 4320 3960 3180 2940 360 720 130 Nothing 55 Nothing
Group 13 Nothing 3500 3350 2940 2520 2420 1250 865 456 Nothing 72 Nothing

My results
Test Tube 1 2 3 4 5 6
7 8 9 10 11 0
(mins) X 52 X 52 43.39 45.60 46.01 58.34 9.47 9.47 X 59.10 2.40 X 59.10 X 52

Change results minutes to seconds
For each group class and my results do Range , Variable , Standard deviation , Variance Graph should be done for whole class results and for your report and compared Experimental procedure

Rate of Reaction Figure 1 Plot of rate of reaction as a function of temperature.

The results were obtained using the conditions described in the Methods Section.

This is the most important part of your report. Interpret the results you obtained and draw general conclusions from them.

Information in the discussion should go from the specific to the general. Below is a typical order of topics which might occur in the Discussion: Major findings (don’t list this as a subheading)
Start the discussion by briefly stating the major findings from the results.

Explain what the results mean. Your experiment is really very limited in scope, so do not claim that you have “proven” or “disproven” something.
Expand on your results

In next paragraph(s) expand your discussion of the results. You might wish to compare them to results from other studies, which you should cite properly.

Introduce some new ideas as the discussion continues it is important to offer some ideas and interpretations.

For example, discuss the implications or your results. For example, why was the conductivity of the water samples from various sources different?

You may wish to suggest new experiments which would add value to the study carried out.

Improvements in experimental design. All experiments have some weaknesses. It is OK to get negative results (e.g. no significant differences between controls and experimental group).

However, you may suggest additional experiments that may include using different methods that will improve the data.

This should only contain the KEY findings from your experiments and no additional comments or interpretation of data.

List any literature which you have cited in the text. List ONLY those references which you have specifically cited. References are listed in alphabetical order.

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