Question

a student studies the effect of ph on the activity of the enzyme amylase by filling three test tubes (a, b, and c) with 1 ml of starch solution, each at a different ph, adding 50 μl of amylase to each test tube, and immediately transferring one drop of the mixture from each test tube to a spot plate. the student then adds a drop of iodine - ki reagent to the drops on the spot plate and repeats the process at one - minute intervals until the solution no longer turns purple, indicating that all of the starch has been digested. the student measures the time taken for the breakdown of starch each time and records the experimental results in the table.

test tube	ph of starch solution	time for breakdown of starch (min)
b	6	20
c	8	20

the student concludes that amylase is most effective in breaking down starch at a ph of 6 and 8. which change should the student make to the experiment to improve the validity of the experimental results?
test a wider range of ph values of the starch solution.
add different amounts of amylase solution to each test tube.
vary the time intervals between each time the process is repeated.
add different amounts of iodine - ki reagent to the mixture on the spot plate.

Explanation:

To improve validity, test more pH values to accurately determine amylase's optimal pH. Other options change non - pH variables.

Answer:

Test a wider range of pH values of the starch solution.