Describe the structures of starch and cellulose, and state how glycogen is related to starch.

How to lay out the answer. Follow the frame, then write it in your own words.

1 · Start with the monomers. Starch and glycogen are polymers of α-D-glucose; cellulose is a polymer of β-D-glucose.
2 · Starch. Two parts: amylose (soluble, unbranched, C1 to C4, 15 to 20%) and amylopectin (insoluble, branched with C1 to C6 links, 80 to 85%).
3 · Cellulose. Straight chains of β-D-glucose joined C1 to C4; the main part of plant cell walls.
4 · Glycogen. Structure like amylopectin but more highly branched; stored in the liver, muscles and brain.
5 · Link to real life. We digest the starch in rice and wheat but not cellulose, which acts as dietary fibre.
6 · Close in one line. So the same glucose unit gives a food store or a building material, depending on α or β links and branching.

Scoring tip: Say α or β for every polymer and name the linking carbons (C1 to C4, C1 to C6).