Structure and nomenclature
With few exceptions (e.g., deoxyribose), monosaccharides have this chemical formula: C x (H2O) y, where conventionally x ≥ 3. Monosaccharides can be classified by the number x of carbon atoms they contain: diose (2) triose (3) tetrose (4), pentose (5), hexose(6), heptose (7), and so on.
The most important monosaccharide, glucose, is a hexose. Examples of heptoses include the ketoses mannoheptulose andsedoheptulose. Monosaccharides with eight or more carbons are rarely observed as they are quite unstable.
Glucose (/ˈɡluːkoʊs/ or /-koʊz/; C6H12O6, also known as D-glucose, dextrose, or grape sugar) is a simple monosaccharide found in plants. It is one of the three dietary monosaccharides, along with fructose and galactose, that are absorbed directly into the bloodstream during digestion. An important carbohydrate in biology, cells use it as a secondary source of energy and a metabolic intermediate. Glucose is one of the main products of photosynthesis and fuels for cellular respiration. Glucose exists in several different molecular structures, but all of these structures can be divided into two families of mirror-images (stereoisomers). Only one set of these isomers exists in nature, those derived from the "particular chiral form" of glucose, denoted D -glucose, or D-glucose.
α-D- β-D- α-D- м
Glucopyranose Glucopyranose Glucofuranose Glucofuranose
Fructose, or fruit sugar, is a simple monosaccharide found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847. Pure, dry fructose is a very sweet, white, odorless, crystalline solid and is the most water-soluble of all the sugars. From plant sources, fructose is found inhoney, tree and vine fruits, flowers, berries, and most root vegetables.
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