Question

Cellulose does not form blue colour with Iodine because ______.

Options

• 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 1

Cellulose does not form blue colour with Iodine because it does not contain complex helices and hence cannot hold iodine molecules.

Explanation:

• Cellulose is a polysaccharide composed of a linear chain of β-linked D-glucose molecules. Plant and algal cell walls rely heavily on it for structural support.
• The blue colour is caused by iodine molecules becoming trapped within the helical structure of starch, forming a complex. When exposed to iodine, cellulose turns colourless.
• This is because it cannot contain iodine. Because cellulose lacks complex helices, it is incapable of trapping iodine molecules and forming a blue complex.