noun, plural: hexoses
A six-carbon monosaccharide
Monosaccharides are the simplest form of carbohydrates. They are classified according to the number of carbon atoms in a monosaccharide. In particular, a hexose is a monosaccharide with six carbon atoms. Monosaccharides may also be classified based on the type of carbonyl group they contain. An aldose is a monosaccharide that contains an aldehyde group (-CHO) at position 1 whereas a ketose is one that contains a ketone (C=O) at position 2. Thus, an aldohexose is a hexose with an aldehyde group. A ketohexose, in contrast, is a hexose with a ketone functional group located in position 2.
Aldohexoses have four chiral centers. Because of that there are 16 possible stereoisomers. Examples of aldohexoses are glucose, mannose, galactose, gulose, idose, talose, allose, and altrose. Glucose is a one of the products of photosynthesis in plants and other photosynthetic organisms. It also serves as an important metabolic intermediate of cellular respiration. In animals, an excess of glucose is stored as glycogen. In plants, glucose molecules are stored as repeating units of sugar (e.g. starch).
Ketohexoses have three chiral centers. As such, there are eight possible stereoisomers. Examples of ketohexoses are fructose, piscose, sorbose, and tagatose.
Word origin: hex(a)- ("six") + -ose (relating to sugars)