When the temperature is colder, the particles move slower, and therefore the breakdown of starch is slower. Also, if the amylase is in conditions way below the optimum temperature, it will not hold its ideal shape and just won’t move; it will become inactive.
Variables:
In an experiment, there are always variables: things that change. Two types of variables exist: Independent and Dependent. An independent variable is a change that I do to the experiment which changes or affects the results which I get. In this case, the temperature would be an example of an independent variable as it is I who changes the temperature where the reaction takes place and affects the speed of the breakdown of Starch. A dependent variable is a change which happens on its own, without me making any changes. For example, the time it takes for the Amylase to turn the starch into maltose and therefore turn the solution of Starch, Amylase and Iodine colourless is a reaction which happens naturally, without me affecting the results in any way.
Control:
There were many things which I did to keep the experiment a fair test and to get correct results. The following show what I did to keep it a fair test:
- I put in the same volume and concentration of amylase in each test tube, which was 1cm³. (To do this, I used a plastic syringe so as to be accurate)
- I put in the same volume and concentration of starch in each test tube, which was 5cm³. (To do this, I used a plastic syringe so as to be accurate)
- I made sure that I had exactly 10 drops of Iodine solution in each test tube using a ‘dropping pipette’.
- Every minute, I shook all the test tubes and made sure that I did it in the same pace in each experiment.
- Since in the starch solution, the starch is insoluble, it doesn’t dissolve properly into the water, and so sinks to the bottom of the jar. I made sure that I shook it well before serving myself so that I got the same concentration of starch in each serving.
- I left the Amylase and the starch solution in the different temperatures of water for five minutes so that they could reach equilibrium.
Method and diagrams:
To carry out this experiment, I intend on using the results from the pre-test to use a range of temperatures which may be suitable for the Amylase to work, to see at which temperature the reaction takes place the fastest. Since in the pre-test, the reaction took place the fastest at 37°C, I decided to make the reaction take place at a range of temperatures going up in 5°C. They are shown as followed: 20°C,25°C,30°C,35°C,40°C,45°C, 50°C and 55°C.
To do this, I placed two test tubes in a beaker filled with water. One test tube contained 5cm³ of starch solution and 10 drops of Iodine. The other test tube contained 1cm³ of Amylase. I also placed a thermometer in the beaker. (I had placed the Starch and the Amylase in after having measured the right quantities in syringes. I used a dropping pipette to put in the 10 drops of iodine indicator). I then heated up the water in the beaker by placing it on top of a Bunsen burner and heating up the water until it reached a temperature of 25°C. I then left the two test tubes in the beaker for 5 minutes, so that they could reach equilibrium. After that, I put the content of both test tubes into 1 test tube and kept them in the water. I counted how many minutes and seconds it would take for the reaction to take place by using a stopwatch. To do this, I watched the colour of the solution of Starch, Iodine and Amylase. (I did this process with each temperature).
I stopped my stopwatch when the solution had turned colourless. At the beginning, in all eight conditions, the reaction had not taken place yet so the Amylase hadn’t turned Starch into maltose yet. This meant that since the starch was still present, the Iodine showed this by turning the solutions blue/black.
When Amylase has completely broken down the starch into maltose, this meant that no more starch was present. To show this, the Iodine turned the solution colourless.
The solution out of the eight solutions which turned colourless the fastest meant that starch was not present meaning that the reaction had taken place the fastest in those conditions. (the reaction had taken place in its optimum temperature).
Protection:
- I wore plastic goggles so that nothing could get into my eyes.
- I was also careful in dealing with the Amylase as it may be dangerous if it comes in contact with open skin
Results table: (raw data)
Results table: (calculated data)
Conclusions
My results show the optimum temperature for the reaction between Starch and Amylase was 40°C because the reaction took place in the fastest time which was 53 seconds. This is the temperature when the reaction was completed the fastest.
I came across problems. The iodine would evaporate then it would look like the solution went colourless so we thought that the experiment had finished before it actually had. The iodine did this because at higher temperatures, the particles moved faster and further apart and so there are more gaps between the iodine molecules therefore you can’t see them. I overcame that difficulty by placing 5 extra drops of iodine in the solution every minute. I did not come across any anomalous results except when I performed the experiment for the first time at 20°C, the solution did not turn colourless even after half an hour, so I had to re-do the experiment at that particular temperature. Perhaps this happened because of the iodine evaporating.
At temperatures lower than 20°C, the Amylase enzymes became in-active and at temperatures higher than 60°C, the enzymes become denatured. This is because at higher temperatures above the optimum temperature, the particles move faster and collide with each other more often and the enzymes loose the shape of their active sites. At lower temperatures, the enzyme freezes and therefore cannot move.
I found that the literature values. The optimum temperature at 40°C and the range of temperatures where the reaction took place without the enzymes being either denatured or inactive was: 20°C≤ temperature ≥60°C.
Evaluation:
The qualitative results were when I relied on my sight to see when the reaction had taken place; when the solution had gone colourless. The quantitative results were the results which told me the reaction had taken place such as the data in seconds.
There were limitations because the water which we heated would cool down and therefore not keep at the same temperature. I did not encounter any anomalous results although I did find that the first time that I did the experiment at 20°C, after twenty minutes, the solution had still not turned colourless, This was perhaps due to the fact that the amylase had formed a lump at the bottom of the test tube and had not mixed with the starch for the reaction to take place.
If I was going to do this experiment again I would improve it by using a different technique of heating than a Bunsen burner to heat up the water, such as a hot plate which was controlled by a thermostat. This would be better because it would keep the temperature constant throughout the whole experiment, which is likely to improve it by getting more accurate results. I could also have improved it by stirring the solution much more frequently so that lumps do not occur. I would do this by using a magnetic stirrer. To avoid the iodine problem in future, I would most definitely keep adding iodine.
I could improve the experiment by making sure the measurements of the volume if liquid in the syringes is correct, so as to get more precise answers as well as making sure there is the exact same concentration of starch in each dose; since it is insoluble, the concentration may have differed in each dose if not stirred a lot each time. Although I did not find any anomalous results, in future I would do the experiment at least twice to make sure my results are accurate and there have been no mistakes. I could make further investigations by finding the optimum temperature of different enzymes like protease and lipase. I could also find the pH of different enzymes.
Bibliography:
