Why cellulose , starch and glycogen are commonly called glucans ?

Explanation

### Step-by-Step Solution:

1. **Definition of Glucans**: Glucans are polysaccharides that are primarily composed of D-glucose monomers. This means that the basic building block of glucans is the sugar molecule D-glucose.

2. **Structure of D-Glucose**: D-glucose has a specific chemical structure represented as C6H12O6. It consists of six carbon atoms, with the arrangement of hydroxyl groups and a carbonyl group that characterizes it as an aldose sugar.

3. **Formation of Polysaccharides**: Cellulose, starch, and glycogen are all polysaccharides formed by linking multiple D-glucose units together through glycosidic bonds.

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