Carbohydrates

By definition, oligosaccharides (oligo = few) are short polymers of 2 to about 10 monosaccharides. Common examples are disaccharides (sucrose, lactose, maltose). Polysaccharides contain hundreds or thousands of monosaccharide units.

Human digestive enzymes (salivary and pancreatic amylase) can only hydrolyze the α-1,4 glycosidic bonds found in starch's amylose and amylopectin. Cellulose consists of glucose units linked by β-1,4 bonds, which require the enzyme cellulase, not produced in the human digestive tract.

Amylose is a linear, helical polymer of glucose linked by α-1,4 bonds. Amylopectin is a highly branched polymer with an α-1,4 linked backbone and α-1,6 glycosidic bonds at branch points occurring approximately every 24-30 glucose units.

Glycogen is essentially the animal equivalent of amylopectin but is more extensively branched (branching every 8-12 residues). This extreme branching creates many non-reducing ends for glycogen phosphorylase to attack, enabling an extremely rapid release of glucose-1-phosphate to meet metabolic demands.

Cellulose is a linear, unbranched homopolymer of glucose. The β-1,4 linkage causes the chain to be straight. Adjacent chains align and form extensive inter-chain hydrogen bonds, creating rigid, high-tensile-strength microfibrils that provide structural integrity to the cell wall.