Final answer:
Starch and cellulose are both polysaccharides made of glucose units, but differences in their glycosidic linkages lead to distinct properties: starch is soluble and digestible due to alpha linkages, while cellulose is strong and indigestible due to beta linkages.
Step-by-step explanation:
The molecules of starch and cellulose are polysaccharides consisting of glucose units. Starch is made of a-D-glucose units, and it has a helical structure due to its alpha-1,4 and alpha-1,6 glycosidic linkages, which make starch soluble in water and capable of being easily digested by humans as an energy source.
On the other hand, cellulose is made up of glucose with beta-1,4 glycosidic linkages, contributing to its rigid and linear structure. These linkages result in the formation of strong, insoluble fibers that confer mechanical strength to plant cell walls but make cellulose indigestible to humans without the appropriate enzymes.
The unique emergent properties of these polysaccharides stem from their glycosidic linkages; cellulose's strength and insolubility make it ideal for structural roles in plants, while starch's solubility and digestibility make it excellent for energy storage.