Starch:

Starch exists in plants as insoluble starch granules in chloroplasts. Every starch granule holds a mixture of two polysaccharide forms, amylopectin and amylose. The Amylose is an unbranched polymer of glucose residues joined in α1-4 linkages. An Amylopectin is the branched form; most of the constituent glucose residues are joined in α1-4 linkages but additional α1-6 bonds occur every 25-30 residues, establishing the branchpoints.

Dextran:

Dextran is a glucose polymer where the glucose residues are mainly linked by α1-6 bonds. Moreover, a few branches also occur. These are classically formed through α1-2, α1-3 or α1-4 bonds depending on the bacterial or yeast species which is the source of the dextran.