Cellulose does not form blue colour with Iodine because
- It is a helical molecule
- It does not contain complex helices and hence cannot hold iodine molecules
- It breaks down when iodine reacts with it
- It is a disaccharide
Answer
(2) It does not contain complex helices and hence cannot hold iodine molecules
Solution
Starch forms helical secondary structures that can hold I2 molecules, so starch gives a blue colour with iodine.
Cellulose (a polysaccharide, not a disaccharide) does not contain complex helices and hence cannot hold I2, so it gives no blue colour.
Answer: (2)