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Biology Coursework Investigation

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Biology Coursework Investigation Aim The aim of my experiment is to investigate how long is needed to digest starch using the enzyme amylase at different temperatures. Introduction I am investigating the time needed for enzymes at different temperatures to digest starch. Enzymes are small protein molecules made in the pancreas and stored in the stomach. They are a biological catalyst that means they increase the rate of reaction in digestion. For enzymes to digest they need to be denatured; this is the term used to describe when enzymes are heated to reach their optimum temperature; when the enzyme is heated over its optimum temperature its bonds are broken and the shape of its active site changes therefore preventing the substrate from fitting into it, as each substrate is specific to one enzyme it will therefore stop reacting. After the enzyme is denatured it can never return to its previous state and because enzymes have a high specificity they can only catalyse one reaction. I am going to test for starch using iodine, when the iodine turns brown this will indicate that the starch is digested. Variables A variable is anything you can measure or change in an experiment. In this investigation there are certain variables, which must be taken into consideration before carrying out the experiment. These include: - The pH of the experiment (input variable) - If the pH is changed this will dramatically affect your overall results. I found this out through the preliminary work. ...read more.


Less equipment to deal with, heat not as extreme and no open flames equal less of a chance for accidents. They are often more effective because the temperature of the water can be controlled more easily and the heat gradually increases, unlike the Bunsen burner where it is very difficult to control the heat. The heat increase is almost instant and low temperatures are hard to achieve because of the severe concentration of heat. Equipment List - Water baths - 2 test tubes - Test tube holder - 2 measuring cylinders - 2 conical flasks - Beaker 100ml - Iodine solution - Starch solution - Amylase solution - Dropping pipettes - Spotting tiles - Thermometer - Stopwatch - Goggles Method 1. First collect and set up the equipment. 2. Put two drops of iodine into each spot on the dimple tray 3. Using one of the conical flasks fill it with water and add a few pieces of ice. 4. Using a blue measuring cylinder measure out 10cm of starch, pour it into a boiling tube and place in the beaker 5. Using a different clear measuring cylinder measure out 5cm of the enzyme solution amylase, pour into a separate boiling tube and place in the same conical flask. 6. Place the thermometer in the beaker and wait for both solutions to reach equilibrium of 10?C 7. Pour the starch solution into the amylase after ensuring that the temperature of both solutions is 10?C 8. ...read more.


Another problem with the pipettes was that there was time for the amylase to act on the starch while the solution was in the pipette, making the timings recorded slightly too small. However, this effect was lessened with most of the temperatures as the mixture was cooling down to room temperature in the pipette. The method by which we tested to see if there was starch remaining did not work entirely satisfactorily. Finally, the procedure of preparing the solutions of amylase and starch for the experiment could have been improved. It is likely that there was some solution left over from the previous repetition of the experiment, making the starch/amylase ratio different each time. This could have been overcome by washing out the test tubes between readings. The volumes of each solution could have been made more accurate by measuring the solutions by using a syringe. Basic improvements I would make if I re-did my experiment would be I would: Use electronic water baths to measure the temperature more precisely, perform the experiment at intervals smaller than 20�C, use a colour meter, repeat each experiment for every temperature more than twice and clean the pipettes and test tubes between each reading. In conclusion, the accuracy of the results was certainly good enough to make a good conclusion. If the experiment had been conducted under more strict conditions and with more advanced instruments, the conclusion would not have been different although the individual results might have been more accurate and the graph might have looked very slightly different. ...read more.

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Here's what a teacher thought of this essay

3 star(s)

*** The candidate has submitted an incomplete report. This report does not contain the candidate's experimental results table, although the results are discussed and evaluated and a graph has been plotted.

The student planned a simple procedure and used suitable equipment. The student planned to take a suitable range of five temperatures and to repeat these readings but several key variables were ignored in the planning stage.
To improve :
There were many scientific inaccuracies in the background material. The student would have benefited from widening the research to include appropriate books and textbooks and selecting relevant material. The risk assessment could have been presented more clearly in a table and the concentrations of the solutions used should be stated.
Carrying Out
Although the student discussed the results these were not present in the report. All raw data for pilot and main experiments are expected to be seen recorded clearly in a table with the correct headings and units. The student would gain no merit for this section.
Analysis and Evaluation
There is a graph plotted but it is not clear whether this is of the candidate's results. The graph should be included in the conclusion of the experiment not at the end. The student has identified a trend in the data and partly explained this using relevant scientific background theory. The student has commented on the reliability of the procedure and suggested some ways of improving the reliability.

Marked by teacher Stevie Fleming 29/05/2013

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