Monosakkaridene

Monosakkaridene are the simplest carbohydrates, consisting of a single sugar unit that cannot be hydrolyzed into smaller carbohydrate molecules. They have the empirical formula (CH2O)n, with n typically between 3 and 7. Common examples include glucose (an aldohexose), fructose (a ketohexose), galactose, ribose, and deoxyribose. They occur freely in nature and serve as essential energy sources and metabolic intermediates.

Monosakkaridene are classified by the position of the carbonyl group (aldose vs ketose) and by their stereochemistry (D- and L-enantiomers). In solution they can exist in ring forms (pyranose, furanose) and undergo mutarotation. In nature, the naturally occurring forms are predominantly D-enantiomers.

They form glycosidic bonds to yield disaccharides and polysaccharides; ribose and deoxyribose are components of RNA and DNA; sugar phosphates participate in metabolism. They also serve as reducing agents due to the free carbonyl group in their linear form, and can be oxidized to uronic acids, reduced to sugar alcohols, or converted into sugar phosphates for energy pathways (glycolysis, pentose phosphate pathway).

Biosynthesis and metabolism: Plants fix CO2 into triose phosphates via photosynthesis; isomerases interconvert aldoses and ketoses; in cells, hexose sugars enter glycolysis or enter the PPP. Catabolic pathways yield ATP and NADH.