What is the basic structural difference between starch and cellulose?
The basic structural difference between starch and cellulose lies in their secondary structures. Starch forms helical secondary structures which can hold I₂ molecules in the helical portion, producing a blue colour. On the other hand, cellulose does not contain complex helices and hence cannot hold I₂ molecules.
Both starch and cellulose are polysaccharides made of glucose units. Starch serves as a store house of energy in plant tissues, while cellulose is a structural component found in plant cell walls. Paper made from plant pulp and cotton fibre is cellulosic in nature.
Explanation
The textbook context explicitly mentions that starch forms helical secondary structures while cellulose does not contain complex helices. This helical structure in starch allows it to trap iodine molecules, giving the characteristic blue colour in the starch-I₂ test. The context does not mention the α and β glycosidic linkage differences, so the answer focuses only on the helical structural difference provided in the source material.