Monosaccharides

These are simple sugars, one of the most important groups of carbohydrates. Based on functional groups, monosaccharides are divided into two classes: aldoses, containing an aldehyde group, and ketoses, which have a ketone group. Carbohydrate chains can have 3 or more carbon atoms (trioses, tetroses, pentoses, hexoses, heptoses, etc.). There are linear and cyclic forms of monosaccharides (furanoses or pyranoses). The most common monosaccharides are D-glucose, D-galactose, D-fructose, D-xylose, L-arabinose. In addition to carbonyl and hydroxyl monosaccharides, there may be a hydrogen atom (-OH) in the molecule, deoxy monosaccharide, an amino group (aminosaccharide), a mercapto group -SH (thiosaccharide), -COOH (uronic acids), etc. In nature, monosaccharides are rarely free (except for D-glucose and D-fructose). They, as monomers, are part of the composition of oligo- and polysaccharides, mixed biopolymers (glycoproteins, glycolipids), combining with each other or with other molecules through glycosidic bonds. Natural mucopolysaccharides actively participate in cellular metabolism. Monosaccharides, participating in various biochemical transformations, supply cells with high-energy compounds, participate in detoxification and the elimination of toxic substances, in the synthesis of amino acids and complex biopolymers. In living cells, the central pathway of monosaccharide biosynthesis is gluconeogenesis. In heterotrophic cells, the source of glucose can be amino acids, lactic acid, and other compound transformation products. When a specific monosaccharide metabolism is disrupted, its concentration increases in the body’s biological fluids. This is an important diagnostic test (galactosemia, diabetes mellitus, melituria, fructosemia).

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė