Carbohydrates are divided into mono-, oligo- and polysaccharides based on their structure. This structure determines the way they are digested. Polysaccharides (starch, glycogen) are digested partially in a mouth by enzyme amylase to oligosaccharides (maltotriose, maltose, dextrin) or monosaccharides (glucose). Additional hydrolysis of polysaccharides is carried in a duodenum by enzyme amylase synthesized in a pancreas. All oligosaccharides (sugar, maltose, lactose, dextrin) are hydrolyzed to monosaccharides (fructose, glucose, galactose) by enzyme complex attached to the membranes of epithelial cells in a small intestine. This enzyme complex includes maltase, sucrose, lactase, isomaltase. At last, monosaccharides are absorbed into blood through the enterocytes in small intestine. It is carried with special protein molecules (transporters) by facilitated diffusion (passive transport) or secondary active transport (cotransport with sodium ions).