Correct Option (c):
The statement "Both of them give colour with iodine" is incorrect. Starch reacts with iodine to produce a characteristic blue-black colour. This reaction is primarily due to the helical structure of amylose, a component of starch, which traps iodine molecules. In contrast, cellulose does not exhibit any colour change when treated with iodine. This is because cellulose possesses a linear, non-helical structure composed of β-D-glucose units, which prevents the formation of an iodine-inclusion complex. Therefore, the iodine test serves as a distinguishing factor between starch and cellulose.
Incorrect Options:
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Option (a): Both starch and cellulose are polysaccharides synthesized by plants. Starch functions as the primary energy storage molecule in plants, while cellulose is the main structural component of plant cell walls.
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Option (b): Both starch and cellulose are polymers. They are classified as polysaccharides, meaning they are large macromolecules composed of many monosaccharide units linked together.
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Option (d): Both starch and cellulose are composed of glucose molecules. Starch is a polymer of α-D-glucose units, whereas cellulose is a polymer of β-D-glucose units. The difference lies in the type of glycosidic linkages (α-1,4 and α-1,6 in starch; β-1,4 in cellulose), which results in their distinct structural and functional properties.