hexosas

Hexoses are a class of simple sugars consisting of six carbon atoms, with the general molecular formula C6H12O6. They include both aldoses, such as glucose, galactose, and mannose, and ketoses, such as fructose. In nature, hexoses predominantly occur in the D-configuration, which is the form most commonly utilized by living organisms, though the L-enantiomers are chemically possible.

In solution, hexoses can adopt multiple isomeric forms. Each hexose has an aldehyde or ketone as the reactive carbonyl group, and five hydroxyl-bearing carbon atoms. These characters lead to extensive stereoisomerism: common aldose hexoses include glucose, galactose, and mannose; common ketose hexoses include fructose. The linear forms can cyclize to form five- or six-membered rings, giving rise to α- and β-anomers through mutarotation; the most common cyclic forms are pyranoses and, less frequently, furanoses.

Hexoses are essential in biology as major energy sources. In humans and many organisms, glucose is the primary fuel for cellular respiration, entering glycolysis and the citric acid cycle. Hexoses are obtained from dietary carbohydrates; sucrose yields glucose and fructose, starch and glycogen supply glucose upon hydrolysis. They are also involved in biosynthetic pathways, including the formation of nucleotide sugars and glycoproteins.

Properties often used in analysis include their status as reducing sugars and their optical activity. The name hexose reflects the six-carbon skeleton; the term was introduced by Emil Fischer in the 19th century.