You can digest starch but you cannot digest ce11u1οse. why?

Cellulose is a lot stronger than starch. Starch is practically useless as a material, but celluose is strong enough to make fibers from, and hence rope, clothing, etc. Cellulose doesn't dissolve in water the way starch will, and doesn't break down as easily.

Your body contains enzymes that break starch down into glucose to fuel your body. But we humans don't have enzymes that can break down cellulose.