Describe the differences in the structure and function of starch and cellulose, explaining how their chemical properties affect their roles in plants.

Starch is a carbohydrate made of glucose units linked by α‑glycosidic bonds, forming a branched or unbranched polymer that is soluble and can be hydrolysed to release glucose.
Cellulose is also a carbohydrate of glucose units but linked by β‑glycosidic bonds, giving a straight, linear chain that forms strong hydrogen‑bonded fibres.
In plant cells starch acts as an energy reserve; it is stored in chloroplasts and amyloplasts and can be broken down when the plant needs glucose.
Cellulose provides structural support; it is a major component of the cell wall, giving rigidity and strength to plant tissues.
The α‑linkages in starch make it readily digestible, whereas the β‑linkages in cellulose are resistant to hydrolysis, which explains why starch is used for energy and cellulose for structure.