Variables:
To keep my experiment as fair as possible and to achieve the best possible results, I will keep the following aspects of my test identical:
Amount and concentration of starch solution, Amount and concentration of amylase solution, amount of iodine solution, amount of benedict’s solution added and pH.
The only variable in my experiment will be the temperature change, as this is the objective of my test.
Throughout my experiment I will be handling chemicals; some of which are dangerous. I will also be using a Bunsen burner throughout the experiment so I will be taking certain precautions. First of all I will wear goggles from the start of my test to the very end. I will use tongs to handle the boiling/test tubes when they are taken out of the hot water bath. If any other safety precautions arise during the experiment, I will take certain measures to make them as safe as possible.
I will set up my experiment as instructed below:
(All boiling tubes above have the same amount of starch and amylase present)
- Using a 100ml measuring cylinder, I will measure out 20ml of both Starch and Amylase solution.
- Put the 20ml of amylase and starch solutions in separate test tubes.
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Next, I will cool/heat an ice/water bath to 5oC (or the chosen temperature) and add a thermometer.
- Wait for the temperature to reach a constant.
- Add both test tubes of amylase and starch into the ice/water bath.
- Wait until both solutions reach the temperature of the ice/water bath.
- When both test tubes are at the correct temperature, add them together into a boiling tube.
- Place the boiling tube into the ice/water bath to keep the temperature constant.
- Once the amylase and starch solutions have been added together start the stopwatch.
- Every 30 seconds, using a pipette, take a sample from the boiling tube and add it into a spotting tile.
- Add 2 drops of iodine solution to test for the presence of starch and wait for the solution to change to a black/purple colour.
- Repeat this every 30 seconds until the solution no longer changes colour; therefore indicating all the starch being converted into glucose.
- Once the iodine stops indicating a black colour, stop the stopwatch.
- Record the indicated time on the stopwatch into the results table below.
- Then, add a few drops of Benedict’s to the solution and put the boiling tube into a hot water bath.
- Wait until the solution has turned a brick red colour; thus indicating all the starch being turned into glucose.
The same process as above should be carried out for every experiment. (A, B, C, D, E, F and G.) When using a water bath instead of an ice bath, set this up by adding water into the bath. Light the Bunsen-burner and keep it on a safety flame until the Bunsen is being used to heat up the water. When the water reaches the correct temperature, pull the Bunsen away to keep the water from overheating.
After completing my experiment, my results are given below in a table. I have also plotted my results onto scatter graph to show the variance in time against temperature.
A 5 14
B 15 11
C 25 8
D 35 3
E 45 9
F 50 13
G 65 No Reaction
In conclusion, from the results of my experiment, I can see that the basic theory behind my prediction was proved correct. From my graph above, I can see that as the temperature increased towards the temperature of the human body (37oC); the reaction time taken for the amylase to digest the starch fully decreased. This is because the amylase was working at its optimum temperature of around 40oC.
At the start of the experiment, the amylase took quite a long time to digest all of the starch present. This is because the enzyme was not working in its ideal range, and so the reaction time was high. As the temperature slowly increased, the reaction time generally got less, which is shown in this part of the graph as a negative correlation. At 15oC, the amylase was still working outside its optimum range, and so as a result, the time taken to digest was still relatively high. As the temperature was still rising, the reaction time was continually falling. At 25oC the enzyme was nearing its optimum range. This is shown in the graph and the results table by the time it took to digest, 8 minutes. Still at this point, the graph shows negative correlation.
When the starch and amylase where tested at 35oC, the reaction time was pretty fast. All the starch was digested within 3 minutes of the start time, as indicated by the graph. This small reaction time shows that 35oC is the optimum temperature for the amylase to work within. In my hypothesis I predicted that around 40oC would be the best temperature, because this is the closest to the normal temperature of our body.
The next temperature tested was 45oC. At this time, the amylase had started to go outside its optimum temperature range once again, therefore the enzymes’ active site becoming damaged by the heat. The heat of the substances would cause the protein structure to break because of the weak bonds holding it together. This damaging of the active site is irreversible, and so slowly the amylase solution would get less and less effective. This is shown by the graph as an increase in the reaction time (positive correlation.)
The next temperature tested was 50oC. At this stage, the amylase took 13 minutes to digest all of the starch, which is a poor time compared to the time it would normally take at its optimum temperature. By now, most of the enzymes’ active site would have been partially denatured, if not fully. The graph continues to rise to show a longer reaction time.
The final temperature tested for the digestion of starch, was 60oC. At sixty degrees centigrade, the amylase had become fully denatured. An irreversible affect. All the starch present in the solution would never be converted into glucose because of the damaged amylase enzyme.
The basic findings from my experiment have been successfully scientifically proven. I have carried out the experiment to the best I possibly could, but given a number of other situations, I feel that I could have made the experiment fairer and more accurate.
The main aspects I feel I could improve my experiment on are: Temperature control and accuracy of results.
To control the temperature of the water baths, for the digestion to take place at the chosen temperature, I could have got better, fairer results by the use of an electric water bath. If I had the use of an electric water bath, I could have kept the accuracy of the test better, resulting in more accurate results.
Another main aspect I could improve on for my experiment is to make the results I received from my test fairer. I could achieve this by repeating each test three times and then taking the average time from the three. This would have given me a more likely result time for the digestion.
I could also increase the time from which I took a sample from each boiling tube. Instead of taking a sample every 30 seconds, I could take a sample every 10 or 15 seconds. This would result in a truer reaction time. I could also take a wider range of temperatures to pinpoint the specific optimum temperature, and the specific temperature that the enzyme denatures. I could do the same experiment changing the pH of the solution, to see how that affects the enzyme and which pH is the best for the conversion of starch into glucose using amylase.
One other aspect to take into account on improving my experiment is my own personal practical skills. I feel that I carried out the experiment to the best of my ability. During the experiment I could have kept a little more level headed and patient, so that I could pay more attention to the task and receive better results. If I had a little more time to complete the experiment, and things where not as rushed, then I feel I could have improved on the accuracy of my results.