Summary
Highlights
Starch is a carbohydrate made of glucose, broken down into glucose by the enzyme amylase. Common foods containing starch include potato, rice, bread, and pasta. The test for starch uses iodine, which turns from orange to blue-black in the presence of starch.
Set up a well plate by adding one drop of iodine to each well. Prepare the amylase solution by mixing 2 cm³ of a buffer solution (e.g., pH4) with 2 cm³ of amylase solution in a measuring cylinder.
Transfer 2 cm³ of starch into a test tube. Add 2 cm³ of the amylase-pH4 buffer solution to the starch and immediately start a timer. Every 20 seconds, transfer one drop of the starch-amylase solution into a well on the plate to observe the color change of iodine. The iodine will initially turn blue-black, indicating starch presence. As starch breaks down, it may turn brick red, and eventually, the iodine will remain orange when all starch has been broken down into glucose. Record the time it takes for the iodine to no longer turn blue-black.
Repeat the experiment using amylase mixed with a pH1 buffer solution, maintaining the same volumes. Add 2 cm³ of the amylase-pH1 solution to 2 cm³ of starch, start the timer, and add drops to iodine wells every 20 seconds. In this scenario, the iodine remains blue-black for a long time, indicating starch is not being broken down because the amylase enzyme has denatured at pH1, preventing it from binding to the starch molecule.