Glycogen is a branched polymer of glucose stored in muscle and liver cells of animals. It is used as a reserve of energy in the form of glucose. Starch is a polymer of glucose used by plants as an energy reserve. Fats, in the form of triglycerides, are also stored as an energy reserve in animals. Although cellulose is a polymer of glucose found only in plants, subtle differences between starch and cellulose make the cellulose polymer more functional as a structural polymer than an energy reserve in plants.

The extensive hydrogen bonding between the chains of cellulose give it structural strength beyond that of any other polysacharide. Hence it is used to form the cell wall of plant cells.

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