Question

Cellulose and starch are both polymers of glucose but fulfil very different functions in cells. Explain the roles and properties of the two polymers and speculate which of their properties may have aided the evolution of their current function. Use the following terms in your explanation: Glycosidic bonds; Starch; Cellulose; Cell wall; Energy storage

Answer 1

Both starch and cellulose are same type of polymers as both are made from the same monomer, glucose and have the same glucose based repeating units.Starch comprises a mixture of amylose and amylopectin where glucose units are bonded together by condensation reactions through glycosidic bonds(1->4).Cellulose molecules contain beta glucose chains which are stronger than amylose and are found only in plants.

Starch is a storage polysaccharide with 1-4 linkages of alpha glucose monomers whereas cellulose is a structural polysaccharide with 1-4 linkages of beta glucose monomers. All the glucose repeating units are oriented in the same direction in case of starch while these are rotated at 180⁰ around the axis of backbone. All these may attribute to the fact that all enzymes that digest starch by hydrolyzing its alpha linkages can't hydrolyze the beta linkages in cellulose, and vice versa.