An experiment was carried out to study the effect of enzyme concentration on the activity of amylase on starch. 3 test tubes P, Q and R were filled with 2 ml of 0.5 %, 1.0 % and 1.5 % of amylase respectively.
2 ml of 1% starch suspension was added into each test tube and the contents were stirred.
Every 2 minutes a drop of the mixture from each test tube was mixed with a drop of iodine solution on a white tile.
All test tubes are immersed in a water bath at temperature of 37oC during the experiment as shown in Diagram 1.
Table 1 shows the results of the experiment.
a) Record the time taken for the starch to be hydrolysed completely in the boxes provided in Table 1.
(b)(i) State two different observations made from Table 1.
Observation 1:In test tube P/0.5% amylase enzyme, the time taken for the starch to be hydrolysed completely is 18 minutes.
Observation 2: In test tube R/1.5% amylase enzyme, the time taken for the starch to be hydrolysed completely is 10 minutes.
(ii) State the inferences from the observation in 1(b)(i).
Inference from observation 1:In test tube P, the concentration of enzyme is low, so rate of enzyme reaction is slow
Inference from observation 2. In test tube R, the concentration of enzyme is high, so rate of enzyme reaction is fast
(c) Complete Table 2 based on this experiment.
Method to handle the variables
Use different concentration of enzyme, that is 0.5%, 1.0% and 1.5% enzyme amylase solutions.
The time taken for the starch to hydrolyse completely
Measure and record the time taken for the starch to hydrolyse using a stopwatch.
Volume of enzyme// concentration// volume of starch // temperature of water bath
Fix the volume of enzyme amylase at 2 ml // Fix the concentration of starch suspension at 1% // Fix the temperature of the water bath at 37oC.
(Write one only and must correspond)
(d) State the hypothesis for this experiment.
As the concentration of enzyme amylase increases, the time taken for the starch to hydrolyse completely decreases / the rate of enzyme amylase activity increases.
(e)(i) Construct a table and record all the data collected in the experiment.
Enzyme concentration (%)
The time taken for starch to hydrolyse completely (minute)
Rate of enzyme amylase activity (minute-1)
f)Plot a graph of rate of enzyme amylase activity against enzyme concentration on graph paper.g) Based on the graph, state the relationship between enzyme concentration and the rate of enzyme amylase activity. Explain your answer.
The higher the concentration of enzyme solution, the higher the rate of reaction, cause by more enzyme molecules in the test tube. More chances of collision occur between enzyme and starch / enzyme substrate- complexes are more formed.
h) Based on the experiment, define operationally what enzyme is.
Enzyme /amylase hydrolyses starch in 37o C into a product that make the iodine solution remains unchanged / yellow, and the rate of reaction is affected by the enzyme concentration.i) The experiment is repeated with test tube R immersed in water bath of 65o C. Predict the time taken for starch to hydrolyse completely in R. Explain your answer.
30-40 minutes / longer than 30 minutes / longer than the time taken when kept at 37oC. This is because in high temperature, enzymes are denatured / the active sites for the reaction are destroyed.