The effect of temperature on amylase


Enzymes are known as biological catalysts, composed out of proteins. This means that they speed up chemical reactions. They are very efficient and used in all processes inn living organisms, including digestion, respiration, and photosynthesis. Enzyme activity depends upon several factors including temperature and pH. In thus investigation I will look at the effect of temperature on the enzyme amylase, which is found in saliva and is used to break down starch into maltose as part of digestion.  One can measure the activity by seeing how long it takes for the starch to disappear by testing for it with iodine.

The purpose of this experiment is to determine the temperature at which amylase is most effective at digesting starch.



Hypothesis As the reaction temperature of amylase solution and starch solution increase, the reaction rate of amylase and starch will increase.

The experiment was conducted with several temperatures: 0°; 20° (room temperature); 30°; 35°; 63°


10ml 0.2% starch

10ml 0.3% amylase

Several drops of Amount of iodine

 Uncertainties: quantities were never precisely measured but compared only by sight


  • spotting tile in which to put the iodine test
  • test tubes, in order to contain liquids
  • Disposable pipettes, in order to transport liquids
  • Thermometer, in order to measure the temperature
  • Heater in order to reach certain temperatures

The independent variable is the temperature. The dependent variable is the time which it takes for the starch to be broken down.


  1. Amylase and starch are poured into two separate test tube. Both should be 10ml and be at room temperature.
  2. The liquids are mixed together and put into a heated or frosting environment in order to reach the desired temperatures.
  3. A spotting tile is used and 5 drops of iodine are dropped into each of the wells.
  4. A small sample of the mixture is taken up by a pipette and is dropped in the first well. The color is noted. The process is repeated every 30 seconds until the iodine changes color, indicating the starch has been digested.
  5. The experiment is repeated several times in order to achieve ultimate accuracy.


The results can be interpreted easily from the following timetable:

Temperature (°C) Time for starch to disappear (s) Average time for starch to disappear (s)
0 120 120
20 70; 120; 20; 20 58
30 100; 100 100
35 15; 17 16
63 500 500



  It can be observed that there is no obvious increase or decrease of the time span concerning the different temperatures. Since the results are rather random, the correlation is probably fairly weak. This could also be explained due to anomalies which occurred during the experiment and hence limited its accuracy. For example, the time between mixing the two liquids and adding them to the iodine was often not recorded and possessed different durations. This allowed the mixture to change its original temperature and either hindered or sped up the chemical reaction involved in digestion.

Another limitation was the fact that the amylase, extracted from our saliva did not possess room temperature as anticipated but was warmer because it was preserved in our bodies. Furthermore, the amylase was preserved in a glass jar in a cold room. It is highly unlikely that it too had a room temperature of 20°. This makes the foundation of the experiment vulnerable as it tempered with the initial approach that both substances should be of equal temperature.

An additional limitation is that the quantity of the amylase and starch were not measured by an exact proportion but rather by sight. This risks a difference between the amount of the substances and contributes to the inaccuracy of the experiment. The measuring has been done in the same fashion during all the experiment rounds. This does not only bring the problem of a wrong proportion between the substances but also between the different trials, making the result for the average time even more unreliable.

Each group conducted a different amount of trials. This made some final results more reliable than others as the mean was more precise and able to generalize. We can only assume that the results of the groups that only made one experiment are right as we have nothing to compare it to. There’s always the risk of it being a special case.

The time span in which the mixture was dropped onto the different iodine wells was not always precisely 30 seconds as the beginning of the experiment and the timer weren’t often synchronized by a couple of milliseconds. If the digestion happened at a fast pace, as it did in room temperature, those would have been vital for the end result. The different rounds were also often a couple of seconds earlier or later than intended as it took a while to drop only the needed amount of the mixture which was fairly small.


The experiment is basically not successful, the test result is not essential and does little to prove my hypothesis.


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