| Criteria | Starch | Glycogen | Remarks |
| Definition | A polysaccharide that serves as the major carbohydrate storage form in plants. | A polysaccharide that acts as the primary carbohydrate reserve in animals and fungi. | Both are glucose polymers, but their structures and storage roles differ. |
| Source | Synthesized and stored in plants (e.g., potatoes, rice, wheat, corn). | Stored mainly in animal liver and skeletal muscle; also present in fungi. | Reflects adaptation to plant vs. animal energy storage. |
| Monomer | Glucose | Glucose | Both consist of glucose monomers linked by glycosidic bonds. |
| Structure | Composed of two components: amylose (linear, α-1,4 linkages) and amylopectin (branched, α-1,4 and α-1,6 linkages). | Highly branched structure with α-1,4 and α-1,6 glycosidic linkages; branches occur more frequently than in amylopectin. | Glycogen is more compact and efficiently mobilized due to higher branching. |
| Branching Frequency | Amylopectin branches approximately every 24–30 glucose units. | Branches approximately every 8–12 glucose units. | Glycogen’s dense branching allows rapid glucose release. |
| Function | Provides long-term energy storage for plants; energy source for herbivores and humans consuming plants. | Provides short-term, rapidly mobilizable energy for animals, especially during fasting or high activity. | Functional differences reflect metabolic needs of plants vs. animals. |
| Solubility | Less soluble in water compared to glycogen due to lower branching. | More soluble in water due to extensive branching. | Solubility relates to accessibility for enzymatic degradation. |
| Degradation | Broken down by amylases (α-amylase, β-amylase). | Broken down by glycogen phosphorylase and debranching enzymes. | Enzyme systems differ between plants and animals. |
