Topic: Biomolecules: proteins, carbohydrates, lipids, nucleic acids· Cell Structure and Function

Cellulose does not form blue colour with Iodine because

1. It breakes down when iodine reacts with it.

2. It is a disaccharide.

3. It is a helical molecule.

4. It does not contain complex helices and hence cannot hold iodine molecules.

Doubtly Asked 30 Oct 2026 NEET UG 2023 Practice test neet Save WhatsApp Report

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Answer: 4. It does not contain complex helices and hence cannot hold iodine molecules.

Key idea: The blue colour of the starch-iodine test comes from iodine molecules held inside the helical coils of amylose.

Cellulose is a linear, straight-chain polymer of glucose (\(\beta\)-1,4 links) with no complex helical structure. Iodine therefore has nowhere to lodge and no blue colour appears. Cellulose is a polysaccharide (not a disaccharide) and it does not break down with iodine, so options 1, 2 and 3 are wrong.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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Cellulose does not form blue colour with Iodine because

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