Starch and glycogen are glucose polysaccharides adapted for energy storage through compact, insoluble, branched or helical molecular structures in organisms.
Coverage 2013–2022 · Updated 15 Jul 2026
Starch stores alpha-glucose in plants, while glycogen stores alpha-glucose in animals and fungi. Their large, compact molecules are relatively insoluble and therefore have little osmotic effect.
Starch contains coiled amylose and branched amylopectin; glycogen is more highly branched. Coiling and branching make the stores compact, and branch ends provide many sites where glucose can be added by condensation or removed by hydrolysis.
| Feature | Starch | Glycogen |
|---|---|---|
| Main location | Plants | Animals and fungi |
| Organization | Amylose coils plus branched amylopectin | More highly branched polymer |
| Shared advantage | Compact, relatively insoluble and readily mobilized alpha-glucose store | Compact, relatively insoluble and readily mobilized alpha-glucose store |
Between meals, enzymes can hydrolyze glucose units from many glycogen branch ends at once, allowing rapid mobilization without storing a large pool of osmotically active free glucose.
Cellulose is also a glucose polymer but uses beta-glucose and forms structural fibres; monomer identity alone does not determine function.
This objective is assessed through structured response, commonly using Outline / Describe / Distinguish.
Outline / Describe / Distinguish / Compare
Build the answer around this relationship: Starch stores glucose energy in plants as amylose and amylopectin.
Confusing glycogen with glucagon or glucose.
Representative question
Outline how and where energy is stored in plants.
B1.1 becomes easy when every answer follows structure -> property -> function. Carbon skeletons and functional groups create molecular diversity. Condensation builds larger molecules and hydrolysis breaks them. Alpha-glucose stores energy as starch and glycogen; beta-glucose forms strong cellulose. Surface carbohydrates enable recognition. Lipids are hydrophobic, triglycerides store energy, phospholipids self-assemble into bilayers, and steroids cross membranes because they are mostly non-polar.
