In: Human and Animal Interaction
Starch, glycogen and cellulose are all polymers of glucose. They differ in the type of glucose present and the bonds which link thr glucose monomers together.
Starch and glycogen are made from alpha-glucose. This is an isomer of glucose in which the hydroxyl (-OH) group attached to carbon number 1 is below the plane of the ring.
Starch is itself composed of two types of polymer:amylose and amylopectin. In amylose, the glucose monomers are linked by 1,4 glycosidic bonds. This means that the bond connects carbon atom number 1 in one glucose to carbon atom number 4 in the other glucose. This produces an unbranched chain of glucose which then folds up to form a coil or helix.
In amylopectin there are two types of glycosidic bonds: 1,4 and 1,6. The 1,4 links are the same as in amylose. In addition some glucose molecules have a glycosidic link from carbon atom number 6 to carbon atom number 1 in a new glucose molecule. This produces a branch point in the amylopectin molecule. Amylopectin is therefore a branched polymer.
Glycogen is similar in structure to amylopectin, but branches more frequently.
Cellulose is an unbranched polymer composed of beta glucose molecules. Beta glucose is an isomer of glucose in which the hydroxyl group attached to carbon 1 is above the plane of the ring. The glucose monomers are linked by 1,4 glycosidic bonds. Hydrogen bonds between adjacent cellulose molecules allow them to form strong fibres, which suite them to their role as the main structural component of plant cell walls.
For more details see: http://www.steve.gb.com/science/index.html http://en.wikipedia.org/wiki/Polysaccharide