Carbohydrates are biomolecules made up of monomers called monosaccharides, which are sometimes referred to as "simple sugars" because they are the building blocks for large, complex carbohydrates or sugars. Monosaccharides containing six carbons, or hexose sugars, include glucose, fructose, and galactose. The hexose sugars are the main fuels of cells, especially glucose. Monosaccharides containing five carbons, or pentose sugars, include ribose and deoxyribose. The pentose sugars are important components of nucleic acids such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) .

The polymers of carbohydrates are disaccharides and polysaccharides that consist of two or more monomers, respectively. Disaccharides are formed by connecting two monosaccharide units through glycosidic bonds, which are covalent bonds and ether-like linkages that connect the hydroxyl groups of two monosaccharide units. Examples of disaccharides are sucrose, lactose, and maltose. Polysaccharides are long chains of monosaccharides connected by glycosidic bonds. Examples of polysaccharides are starch, cellulose, and glycogen. Polysaccharides that yield a large number of monosaccharide units on hydrolysis are called polysaccharides.

In summary, the monomers of carbohydrates are monosaccharides, and the polymers of carbohydrates are disaccharides and polysaccharides. Disaccharides are formed by connecting two monosaccharide units through glycosidic bonds, and polysaccharides are long chains of monosaccharides connected by glycosidic bonds.