hexoses

Hexoses are a class of monosaccharides that contain six carbon atoms. They include aldoses, which carry an aldehyde group, and ketoses, which carry a ketone group. The most common examples are the aldohexoses glucose, galactose, and mannose, and the ketohexose fructose. Hexoses exhibit multiple stereoisomeric forms, and natural sugars are predominantly in the D- configuration.

In solution, hexoses exist in equilibrium between linear and cyclic forms. Cyclization produces five- or six-membered rings, known as furanose and pyranose forms, respectively. The ring can adopt alpha or beta anomeric configurations as the molecule rotates around the anomeric carbon, a process called mutarotation.

Hexoses play central roles in metabolism and biosynthesis. Glucose is a principal energy source in glycolysis and cellular respiration. Hexoses can be interconverted into other sugars and serve as building blocks for disaccharides such as sucrose (glucose–fructose) and lactose (glucose–galactose), as well as for polysaccharides like starch and glycogen (energy storage) and cellulose (plant structural material).

Occurrence and properties: hexoses are widespread in nature and common in fruits, honey, and many dietary carbohydrates. Many hexoses are reducing sugars and can participate in glycosidic bond formation, giving rise to a wide range of glycosides and complex carbohydrates.