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LABORATORY REPORT GUIDELINES FOR STUDENTS You must produce a laboratory (lab) report for each practical you carry out. The report should focus on the presentation, interpretation and analysis of the experimental results achieved in the laboratory practical • ● Format: the lab report should be written up using word processing software e.g. Microsoft Word Number of Words: 800-1000 (plus calculations, diagrams, references etc.) Presentation: your report should be professionally laid out, with all diagrams and tables clearly labelled. The report should be completed in good English. Your report should include the following sections: 1. Theory & Aim A short summary of the objective of the experiment and the hypothesis being investigated. Extensive background material is not required. 2. Materials, Methods & Safety This section should be written in continuous prose (rather than as bullet or numbered points), in the past/passive tense and in the third person. It may also contain diagrams. This section should also include any specific health and safety precautions undertaken in the experiment. 3. Results This section should contain any graphs, tables, charts etc that you have plotted or constructed from the results recorded from the experiment. All graphs, tables, charts etc. should have a number and a short title to show what is represented. Tables should be presented beneath the number and title and should be clear and easy to look at. A short paragraph beneath the table may comment on some trends that are shown by the results. Use IT software to construct and fill your tables and/or to draw graphs etc. Present your results from experiments in a suitable form. 4. Discussion, Interpretations & Conclusions Your discussion section is one of the most important sections of your report. Here, you write about your results and try to interpret what has happened during the experiment./n PRACTICAL SUMMATIVE ASSESSMENT: AN INVESTIGATION INTO THE EFFECT OF PH ON THE ACTIVITY OF ENZYMES Introduction Catalase in an enzyme that breaks down hydrogen peroxide to water and oxygen. The reaction can be summarised by the equation below: 2H2O2 2H2O + O2 Catalase is found in potato tissue. You will be investigating the breakdown of hydrogen peroxide at a number of different pH values in order to test catalase activity. You will cut thin discs from potato tissue and put them in different pH buffer solutions. You will then put them in hydrogen peroxide diluted with different buffer solutions. As the reaction takes place the oxygen given off by the experiment will cause the potato discs to rise, and you will time them to work out the reaction rate. Equipment List A fresh potato Scalpel or sharp vegetable knife Board or tile (for cutting potato on) 5 x flat bottomed specimen tubes Size 4 cork borer Forceps, tweezers or mounted needles 50 cm³ hydrogen peroxide solution (per group) 5 small beakers labelled with pH values 4.0, 5.0, 6.0, 7.0, and 8.0 A sheet of graph paper (per individual student) A beaker of distilled water Paper towels Safety glasses Stopwatches Chinagraph pencil or marker pen A beaker labelled "waste" 2 x 5 cm³ syringes or measuring cylinders Glass rods Notes: • Students may work in groups of 2 or 3, but each student must record the results of their experiment in their own individual notebooks. Each student must then write their own independent report. You are required to carry out the procedure below twice so that you can check the reliability of your results. This means that you may have to thoroughly wash your test tubes between replicates or use fresh clean tubes for your duplicate readings. Health & Safety Wear eye protection and laboratory coats. Hydrogen peroxide is corrosive. You must wear eye protection (safety glasses) when using it. If any comes into contact with your skin wash it immediately using hot water or running tap water. The buffer solution with pH values 4.0, 5.0, 6.0, 7.0, and 8.0 is classed as a low hazard. Procedure And d 052197 017 S 1. Place the graph paper on the tile and the potato cylinder on the graph paper. Use the scalpel to cut discs of potato tissue that are all about 1mm thick by cutting across the cylinder. You will need 10 discs for the investigation. 2. Place two discs into each of the small beakers provided, which contain buffer solutions of pH 4.0, 5.0, 6.0, 7.0, and 8.0. 3. Use a 5 cm³ syringe to put 5 cm³ of the hydrogen peroxide solution into the flat bottomed specimen tubes. 4. Use a clean 5 cm³ syringe to put 5 cm³ of the pH 4.0 buffer solution into one the flat-bottomed specimen tubes. Use the glass rod to stir the contents of the tube to mix the buffer solution and the hydrogen peroxide. Rinse out the syringes and wash the glass rod using distilled water (for use later at step 7). 5. Use the pair of forceps to place one of the discs from the beaker with the pH 4.0 buffer solution into the specimen tube. As soon as the disc reaches the bottom of the tube, start the stopwatch. Watch carefully and stop timing as soon as any part of the disc lifts of the bottom of the tube. Record the time, in seconds, in your notebook. 6. Remove the disc and place it in the waste beaker. 7. Repeat step 5 with the second disc from the beaker containing buffer solution at pH 4.0. Record the time as before. 8. Repeat steps 3 to 7 with the remaining discs using the other buffer solutions at the other pH values. Record the time as before. 9. Now that your experiment is complete you should calculate the mean time taken for the discs to rise at each pH value. Record these values into your laboratory notebook. 10. Using the mean time you should calculate reaction rate in the final column (100 divided by number of seconds). 11. Plot the results in a suitable form. 12. Write a report of the experiment and discuss your results, showing trends or patterns you observed. Compare your results with published results in text books or journals. Don't forget to discuss the experiment and results as a whole, for example include a part on how pH affects enzymes in general, how good were your experimental procedures, how could you improve the accuracy of your results, what were the limitations of the experiment, were there any anomalies in the results. Also remember to reference your work using the Harvard system, if you quote information from published sources. 11.Plot the results in a suitable form. 12. Write a report of the experiment and discuss your results patterns you observed. Compare your results with publi books or journals. Don't forget to discuss the experime whole, for example include a part on how pH affects enz good were your experimental procedures, how could yo of your results, what were the limitations of the experim anomalies in the results. Also remember to reference your work using the Harva information from published sources. Seconds trial I trial 2 PH 4 35 40 PH5 31 28 PHG 26 24 PH 7 29 4029 PH 8 23 22 דו

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