Answer to Question #283274 in General Chemistry for Sonal

Question

Amylase was added to the test tube with starch solution, and placed in a thermostat at 37 ° C for 10 minutes. Then the contents of the tube were divided into two parts. Lugol's reagent was added to the first tube, and Fehling's reagent to the second after 10 minutes Lugol's reagent. What result can you get? Explain?

Answer 1

Amylase is an enzyme which catalyses the breakdown of Starch into Amylose and Amylopectin. Starch is a polysacharide which is made up of Amylose and Amylopectin. Amylose is a polymer of glucose. Lugol's reagent is a mixture of iodine and potassium iodide.

The result of containing fehling's reagent gives a negative test as starch is depleted when amylase breaks starch to reducing sugars while the solution with Lugol's reagent gives reddish-brown colour due to presence of Amylopectin therefore a positive test.