Animals also store energy as polymerized, highly branched glc called glycogen. Intestinal microbes in termites and ruminants can digest so it can be used symbiotically in these animals. Also, adjacent chains can form intermolecular H bonds. This results in cellulose fibers having high tensile strength. See fig 9-17 p. 307.
Chitin is exoskeleton material.
It's just like cellulose except the monomer is the 2 N acetyl derivative of glc. The CHO is like chitin except every other monomer is bonded to the 2-OH of lactic acid which in turn is bonded to pentapeptide. For important heteropolymers see P. 309. Lipids Ch 11. A functional or operational definition rather than a structural definition.