**4. Complex carbohydrates**

Complex carbohydrates (polysaccharides) are polymers of the simple sugars . Starch is the principal polysaccharide used by plants to store glucose.

(**n** is the number of repeating glucose units and ranges in the 1,000's)

Starch

Zeeman *et al*., 2010 reviewed the role of starches in plants. Starch breakdown commonly occurs when seeds germinate. Starch is also involved in malting (Halford *et al*., 2010). Glycogen, also a polymer of glucose, is the polysaccharide used by animals to store energy. Another important polysaccharide is cellulose. Cellulose is used as a structural molecule to add support to leaves, stems, and other parts of plants. Although cellulose can't be used as an energy source in most animals, it provides essential fiber in the diet. Cell wall polysaccharides vary with plant groups and can include cellulose, xyloglucan, arabinoxylan, and pectin. In plants they make up the primary biomass and contribute to fiber in the human diet. This area has been reviewed by Scheller & Ulvskov, 2010; Fontes & Gilbert, 2010.
