Question

Which of the following statement is incorrect w.r.t. starch?

• A. Starch consists of unbranched amylose and branched amylopectin
• B. It is a polymer of $\alpha –D–$glucose
• C. Successive glucose units are linked together by $\alpha 1\to 6$ linkage and at branching $\alpha 1\to 4$
• D. Starch turns black with iodine

Answer 1

The correct option is C Successive glucose units are linked together by $\alpha 1\to 6$ linkage and at branching $\alpha 1\to 4$

Starch is a polymer of α-glucose. Starch is made up of amylose and amylopectin. Amylocpectin is a branched chain with several glucose residues joined by 1,4-glycosidic linkages and at branching is by 1,6-glycosidic linkages. Successive glucose units are linked together by α $1\to 4$ linkage and at branching α $1\to 6$ linkage is present. Both amylose and amylopectin have α-D-glucose as their monomer units. Iodine turns blue-black on reacting with starch.