Water soluble component . It is long unbranched chain polymer.It contains 200-1000 $\alpha -D-(+)-$ glucose involving C1 - C4 glycosidic linkage .
Constitutes about 15-20 % of starch .
Water insoluble component .
It is a branched chain polymer.
It is a branched chain polymer of $\alpha-D$ glucose units in which chain is formed by C1-C4 glycosidic linkage whaere as branching occurs by C1-C6 glycosidic linkage .
Constitutes about 80-85 % of starch .