hexose

Hexose is a monosaccharide containing six carbon atoms. Its general formula is C6H12O6, and hexoses include both aldohexoses (with an aldehyde group) and ketohexoses (with a ketone group). In aqueous solution, hexoses exist primarily in cyclic forms: six-membered pyranoses and five-membered furanoses, which are in equilibrium with the corresponding linear forms.

Hexoses have several stereocenters, giving many possible isomers. In nature, the D-enantiomers predominate over the L-enantiomers. When hexoses cyclize, they can adopt alpha or beta anomeric configurations, a phenomenon known as mutarotation.

Biological relevance: Glucose is the most important hexose for energy metabolism in many organisms. Other common hexoses include galactose and mannose (epimers of glucose) and fructose, a ketohexose. Hexoses serve as monomers for larger carbohydrates such as starch, glycogen, and cellulose, in which glucose units are linked in different glycosidic bonds. They are transported and metabolized through pathways such as glycolysis, and can be modified to form various derivatives.

Examples and derivatives: D-Glucose, D-galactose, D-mannose, and D-fructose are among the best characterized hexoses. Deoxyhexoses and aminohexoses also occur in biological systems, contributing to glycoproteins and glycolipids.

Occurrence: Hexoses are common in fruits, honey, and plant tissues; they are produced by photosynthesis and are rapidly interconverted by metabolism and enzymatic processing.