Question

What are the main structural similarities and differences between glycogen and cellulose? How does glycogen's structure facilitate its use as a rapid energy reserve that can be used ultimately to make ATP?

Answer 1

Cellulose and glycogen both are polymers of glucose monomer. Glucose consists of 6 carbon atoms arranged in a ring structure. Glucose monomers can be connected with each other at different carbons to give rise to different structures.

In glycogen, glucose are connected at first and fourth carbons by 1,4-glycosidic linkages or at first and sixth carbons by 1,6-glycosidic linkages. Cellulose has 1,4-glycosodic linkages. Glycogen has alpha linkages whereas cellulose has beta linkages. Glycogen is a branched structure important in storing energy. Because of the branched structure it has many ends from which molecules can be rapidly degraded into glucose. The alpha linkages in glycogen make it hydrophilic. Cellose is very insoluble because of beta linkages. Hence glycogen is a form of energy storage which is quickly mobilised to meet body needs.