Answers

2015-08-13T17:24:51+05:30
Cellulose is a carbohydrate gives some energy but not useful as food for man.        that is the reason.

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2015-08-13T18:25:19+05:30
Cellulose  cannot be digested in the highly developed organisms like humans.plants have a specialized system of digesting cellulose.
    hence though cellulose  is a carbohydrate it not useful as a food material for humans
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