What is the overall structure of the material?
Starch is made of long chains of glucose molecules with branches in places. These chains are packed together in plastids to form starch grains. Starch contains a mixture of 25-30% amylose (unbranched chains of α-glucose molecules linked by 1-4 glycosidic bonds) and 70-75% amylopectin (branched chains with 1-6 glycosidic bonds).
Starch molecules arrange themselves in the plant in semi-crystalline granules. Each plant species has a unique starch granular size: rice starch is relatively small (about 2μm) while potato starches have larger granules (up to 100μm).
amylose vs amylopectin:
the glucose molecules are linked in a "linear" fashion; however, the tetrahedral chemistry of carbon (and the bond angles that result from this chemistry) gives amylose an overall spiral shape.