Monosakkaridia

Monosakkaridia, or monosaccharides, are the simplest units of carbohydrates and cannot be hydrolyzed into smaller carbohydrate components. They are the fundamental building blocks from which more complex carbohydrates, such as disaccharides and polysaccharides, are synthesized. In solution, most monosaccharides adopt ring forms and contain a carbonyl group (aldehyde or ketone) along with several hydroxyl groups.

Classification of monosaccharides is based on the number of carbon atoms: triose (3), tetrose (4), pentose (5), hexose (6), and heptose (7). The most biologically important examples are hexoses such as glucose, fructose, and galactose, and pentoses such as ribose and deoxyribose. Aldoses have the carbonyl group at the end of the chain, while ketoses have it within the chain. Natural monosaccharides generally exist as D-enantiomers, with L-enantiomers being rare in nature.

Functionally, monosaccharides provide immediate energy through cellular respiration and serve as essential precursors for other biomolecules. Glucose is a central fuel in glycolysis, while ribose and deoxyribose are components of nucleotides in RNA and DNA, respectively. Monosaccharides can link through glycosidic bonds to form disaccharides (for example, sucrose, lactose, and maltose) and larger polysaccharides such as starch, cellulose, and glycogen.

Natural occurrence is widespread in plants and animals, with dietary sources including glucose, fructose, and galactose. Their structural diversity and chemical reactivity underlie many biological processes, including energy metabolism, nucleic acid synthesis, and glycan formation.