Question

Ions of iodine react with enzyme amylase and used as quantative test for measuring quantity of amylase. However, ions of iodine react with enzyme amylopectin very slightly. Why.

Answer 1

Plants reserves energy in the form of starch. There are two types of starch is present in plant cell- amylose and amylopectin. The amylose is the linear in which disaccharide units of glucose molecules are connected by α(1→4) glycosidic bonds whereas the amylopectins are branched molecules in which disaccharide units of glucose molecules are connected by α(1→4) glycosidic bonds and brached at every 24 to 30 glucose units by α(1→4) glycosidic bonds. When we eats food which is derived from the plants the starch is breaks into small units of glucose which is further used by the system for metabolic processes like glycolysis.

Amylose forms blue-black colour in the presence of the iodine because it forms helices with iodine molecules whereas the amylopectin which is branched at many branching points and forms very small helices with iodine because of branching that’s why it gives red violet colour with amylopectins. Ions of iodine react with enzyme amylopectin very slightly because of branching of amylopectins.

When the colour is not produced in the presence of iodine it means the starch is fully hydrolysed by amylase.At this time we can calculate the enzyme by measuring the time for amylase to hydrolyze starch at that time there is no blue black colour is produced (it remains orange color). Then we can go for calculation of the rate of enzyme in controlled reaction (use buffer for maintaining pH) by using formula- 1/time.