Passage IV

Amylase is an enzyme that speeds up the breakdown of starch into smaller carbohydrates (such as maltose).

A starch solution, an amylase solution, and several buffer solutions (solutions that maintain a constant pH) were prepared. Two experiments were done using these solutions and the following tests:

Iodine test: 3 drops of a brown KI₃ solution is added to a sample solution. If starch is present in the sample solution, the solution will turn from brown to black.

Benedict's test: 1 mL of a blue solution containing CuSO₄ is added to a sample solution. The solution is then heated in a boiling water bath for 3 min. If maltose present in the sample solution, the solution will turn is from blue to orange.

Experiment 1

Each of 7 test tubes was filled with 5 mL of pH 7.0 buffer solution. Different amounts of starch solution and/or amylase solution were added to each tube. The solution in each tube was then diluted to 10 mL with the buffer solution (so the final pH was 7.0 in each tube). Each tube was then incubated at a constant temperature for 10 min. The iodine and Benedict's tests were then each done with 2 mL samples drawn from each tube (see Table 1).

Experiment 2

Seven test tubes were filled and tested according to the procedure used for Tube 3, except that for each tube, a different buffer solution was used (see Table 2).