Which one of the following statements regarding starch and cellulose is not correct?

1. Both of them are of plant origin
2. Both of them are polymers
3. Both of them give colour with iodine
4. Both of them are made up of glucose molecules

Explanation

Option (c) is correct

• Starch gives a characteristic blue–black colour with iodine, which is used to detect its presence (for example, rice turning blue–black in the iodine test). Both starch and cellulose are plant polysaccharides made of glucose units. However, only starch shows this colour change because iodine forms a complex with the helical amylose component of starch. Cellulose does not form this complex and therefore does not produce a blue–black colour with iodine.

Answer: (c) Both of them give colour with iodine