Starch consists of two polymeric units, namely

Options

A. inulin and pectin
B. glycogen and cellobiose
C. cellulose and cellobiose
D. amylose and amylopectin

Answer

D

Explanation

Starch is a polymer of `alpha - D -(+) -` glucose and consists of two components-Amylose and Amylopectin. Natural starch has appoximately 10 - 20% of amylose and 80 - 90% of amylopectin.
Amylose is water soluble component which gives blue color with iodine.Chemicall amylose (polysaccharide) is a long straight (unbrached) chain having only `alpha - D - (+) -` glucose units joined together by `alpha`-glycosidic linkages involving `C1` of one glucose and `C4` of the next.it can have 100 - 3000 D-glucose units i.e., its molecular mass can range from 10,000 to 5000,000.
Amylopectin is a branched chain polysaccharide insoluble in water which does not give blue color with iodine. It is composed of chains of `25-30 D`-Glucose units joined by `alpha-D-` glycosidic linkages between`C-1` of one glucose unit and `C-4` of the next glucose unit (similar to amylose). However, these chains are connected with each other by 1, 6-linkage.