Hexose, also known as six carbon sugar, is a monosaccharide containing six carbon atoms.Hexose is the most widely distributed and abundant in nature, and is also the most closely related to the nutrition metabolism of the body.
The chemical formula of hexose is C6H12O6The 6-carbon sugar containing aldehyde group in position 1 is called hexaldose, and the hexose containing ketone group in position 2 is called hexketose.Five of the six carbon atoms of hexose are connected with hydroxyl (- OH), and the remaining one belongs to an aldehyde group (- OH) or ketone group (- CO -).The carbon at position 1 of glucose molecule belongs to an aldehyde group, so glucose is an aldose ALDOSE (ALDO=aldehyde).The second carbon of fructose belongs to a keto group, so fructose is a ketose.
Glucose canmonosaccharideExists, but most of them exist in the form of polysaccharide, and can also be composed ofGlycoside；fructoseIt is the sweetest sugar in the sugar category to formDisaccharideThe form of is common;GalactoseAlso withlactose、RaffinoseorAgarIsodisaccharidesTrisaccharideOr polysaccharide form is common.These three hexoses are the most important for human nutrition and the main source of energy for human body.[1]
Structure of glucose and mannose
The aldehyde or ketone group in hexose will react with the hydroxyl group in the molecule to form a semi acetal or semi ketal ring structure.For glucose, this reaction connects the carbon at position 1 with the carbon at position 5 through an intermediate oxygen atom, and generates a hexagonal ring (pyranose ring) structure composed of five carbon atoms and one oxygen atom, which is called pyranose.For fructose, this reaction connects two carbon atoms and five carbon atoms through one oxygen atom to form a pentagon (furan ring) structure composed of four carbon atoms and one oxygen atom, which is called furanose.The ratio of hexose chain to ring structure depends on the molecular structure and other conditions.
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In the ring structure, glucose has two isomeric forms, and they can be seen in nature.The hydroxy group of carbon 1 in Γ - glucose is located below the circular plane, while the hydroxy group of carbon 1 in β - glucose is located above the circular plane. This parameter greatly affects the composition of polysaccharides.The circular fructose also has two isomeric forms, namely, Γ - and β -.[2]
