Question

Which of the following statements is/are incorrect?

I. Amylose does not give blue colour with $I_2$ solution.

II. Amylopectin gives blue colour with $I_2$ solution.

III. Amylum is present in wheat, maize, rice, potatoes, barley, sorghum etc.

IV. Amylose is linear polymer of D-glucose units.

• A. I and II only
• B. III and IV only
• C. I and III only
• D. II and III only

Answer 1

The correct option is A I and II only

Option (A) is correct.
I. Amylose gives blue colour with $I_2$ solution. Amylose is a linear chain polymer that forms crystalline structures in the starch. When reacted with iodine, the iodine molecules enter the cavities of the crystalline structures and reflect the characteristic blue colour. When the starch solution is heated, these crystalline structures are disrupted forming a random chain, and hence, the loss of colour. Upon cooling, amylose has the ability, to refold into its crystalline form and hence the colour is regained to blue upon cooling.
II. Amylopectin does not give blue colour with $I_2$ solution.