Preliminary Work: Before carrying out the actual experiment I carried out preliminary work I order to test certain conditions and work out the correct amounts of each substance to use. As a result of these investigations I found that using too much of the amylase substance will create less useful results than if you use smaller amounts. However using too much starch solution does not affect the results as the amylase is designed to cope with such situations. I also found that the technique that I used for applying the amylase to the starch was ineffective and a likely cause for my using excessive amounts of it and I have therefore revised my techniques since then in preparation for the actual investigation. Having taken the time to complete preliminary work I now feel that my experiment will be more effective and my results more reliable.
Equipment: The equipment that I intend to use in this experiment are listed in bullet points below…
- Pipette
- Syringe
- White Tile
- Bunsen Burner
- Gauge
- Safety Mat
- Tripod
- Glass Beaker
- Plastic Beaker x3
- Stop Watch
Plan: Below I have listed in steps the method that I intend to use for carrying out my experiment…
Step 1: Before beginning the experiment ensure that all equipment needed is present and correct and don an apron and goggles for safety measures.
Step 2: The first task that I will do is to gently heat the amylase and starch solution first at 10°C, then 20°C, then 30°C, then 40°C, then 50°C, and finally 60°C. I chose not to go to 100°C since if I did this there would be a danger that the starch element of the solution may begin to breakdown into a maltose solution. I would do this using a Bunsen burner set onto a gentle flame.
Step3: I would then begin the actual data recording. The first result is done at room temperature therefore the amylase/starch solution would not need to be heated, I would simply drop a small globule of the iodine solution (which detects the presence of starch) onto the white tile using a pipette and add a drop of the starch/amylase solution using a syringe. I would now beginning timing and record the colour change that occurred.
Step 5: Each time I will rock the syringe backward and forwards to mix the amylase and starch solution together and then push one droplet of the solution onto the droplet of iodine below. I would repeat this 5 times, each with a higher temperature starch/amylase solution, each time repeating 30 seconds after the last to provide sufficient time for a colour change to occur. I would also make sure that I took up exactly 10 cubic cm of the starch suspension and 5 cubic cm of amylase into the syringe.
Fair Testing: In order to ensure that the experiment is a fair one I will repeat it 5 times. I will control the variables to the best of my ability, ensuring that I use the stopwatch accurately when recording time and also ensuring that the temperatures I get for the amylase/starch solution are as accurate as possible using the available equipment.
Safety: To ensure that the experiment is a safe one I will wear an apron and especially wear goggles when handling the iodine since it is potentially dangerous irritant. I will ensure that I am behaving sensibly around the Bunsen burner and other dangerous apparatus and I will endeavour to act sensibly at all times during the course of the experiment.
Diagram: Below is a diagram of the equipment that I will use, as it will be set out during the experiment…
Observations: As I was carrying out the experiment I made several observations and had to make several changes regarding the way in which I carried out the experiment. The first and most important of which is that I chose not to heat my starch solution using a Bunsen burner and instead opted to use a heated water bath since this was easier to maintain at a certain temperature and generally easier to control. The change that I made was in the timing between the addition of the starch solution to the iodine, instead of adding it every 30 seconds as I had written in my plan I chose to do it at 20 second intervals since this gave me better results. I discovered this when I first began the experiment and I found that the results that I was getting were not particularly useful since the amylase was not acting on the starch quick enough. However when I changed the timing of the intervals I found the results were far more efficient and useful to my investigation. It took several attempts after this to get the best results that I could since I had failed to master the use of the pipette and repeatedly found that I was adding too much amylase/starch solution to the iodine which also would have made my results invalid.
After much deliberation the class has decided that the results that were gathered are not sufficient or reliable enough and therefore I will conduct the remaining part of this investigation using the alternative set results that my science teacher supplied me with. These results are listed below…
Analysing Evidence: A graph to show the relationship between the temperature of the starch solution and the time that it took for the amylase for digest it.
Temperature (°C)
Analysis: The above graph shows that there is definite correlation between with the temperature of the starch and the rate at which it is digested by the amylase. This is because the amylase enzyme has an optimum temperature at which it works best. The optimum conditions that the amylase is usually accustomed to is between 37-40°C and if you look at the graph you will notice that the starch was digested in 5 minutes at 40°C, the quickest time that I registered in the experiment. I also noticed that before and after the optimum temperature the amylase fails to digest the starch at all this is because any higher and the amylase enzyme itself will begin to breakdown, rendering it useless, and any lower and the enzyme will work at a slower rate, reducing its effectiveness a great deal. One of the interesting things that I found when analysing the data was that the reading for 20°C which registered as taking 20 minutes for the starch to be digested by the amylase. This is an anomalous result and I have circled this on the graph. This faulty reading was probably due to human error, however if the reading had been performed correctly it may suggest that perhaps the equipment, solution or amylase enzyme were faulty. The readings data that I have gathered from the experiment support my prediction, which was that the enzyme would be most efficient at room temperature and less effective and in more extreme conditions.
Evaluation: I will now proceed to evaluate my investigation explaining what went well, what did not and possible improvements and methods of gathering more efficient evidence…
Accuracy – The accuracy of the investigation is determined by a number of things, one of which is how well I read the instruments. This is difficult, especially with the thermometer, which is probably the most inefficient piece of equipment that I used. This is because it relies purely on the human eye to interpret each reading, which is not very reliable at all. The stopwatch, used to take the time of each reading is also not particularly accurate since it to relies on human reflexes and I should have really allowed for this, something which I failed to do but perhaps could include next time. However I did manage to make sure that each instrument was zeroed before I began using it, something that could be potentially damaging to the accuracy of the experiment. I chose to use a standard thermometer however if the opportunity had been available to me, I would have chosen to use a digital thermometer and do not rely on the human eye to take the reading.
Precision – The smallest units for each instrument were as follows…
- Seconds: Stopwatch
- °C: Thermometer
- Ml: Glass beakers
I believe that measurements were precise enough for the investigation to be carried out correctly, although slightly more accurate readings would have been more than welcome. I have ensured that the measurements are featured on my results.
Reliability – The results for the first time that I carried out the investigation were not similar when repeated ands the results provided by our teacher were not repeated, therefore one point of improvement would certainly be to repeat the experiment several times in the future, since this would ensure that all of the results follows a similar pattern and also make certain that a definite pattern does actually exist.
Anomalous Results: I found one anomalous result in the graph and table and table and when I created the table I made sure that I highlighted this to make sure that it was significant on the page and taken into account when writing up my findings.
Procedure – When carrying out the experiment I made sure that the procedure was sequenced correctly and carried out as close as possible to my original plan. I made sure that the test was a fair one by using the same amount of starch solution and amylase enzyme every time and ensuring that the temperature of the solution was correct to the planning. The range for my independent variable was 0 - 60°C, I believe that this was sufficient since it provided me with evidence that the optimum temperature that the enzyme worked at was body temperature and also showed that it wasn’t as effective at the higher or lower temperatures. The interval for the independent variable was 10°C. Improvements – There are a number of changes that I feel are necessary to improve the experiment, the fist being to repeat the investigation several more times to ensure that the curves and gradients that I find on the graphs and correct and not anomalous. The second change I would make would be to gather more results within the range especially around the body temperature, since this would provide more precise results and find out more accurately what the optimum temperature that amylase works out is. I would also have chosen to use a digital thermometer and do not rely on the human eye to take the reading and would therefore provide more accurate results.
Validity – I believe that the investigation that I have carried out was a valid one since the variables that I have chosen tested the aim very well. I do not think that I would have collected such good results had I not use the variables that I did.