Aldoheksosa

Aldoheksosa, or aldohexose, is a monosaccharide with six carbon atoms and an aldehyde group at carbon 1. It belongs to the class of aldohexoses and has the general linear formula HOCH2-(CHOH)n-CHO, with four stereocenters at C2–C5 (n = 4). Because of these four chiral centers, there are 2^4 = 16 possible stereoisomers, which occur as enantiomeric D- and L-forms; in biology, the D-forms predominate.

Common examples of aldohexoses include D-glucose, D-galactose and D-mannose. Other members of the family comprise D-idose, D-gulose, D-allose, D-talose, and D-altrose. Each aldohexose has a distinct configuration at its chiral centers, giving rise to different physical and biochemical properties.

In solution, aldohexoses readily cyclize to form hemiacetals. The six-membered pyranose form is most common for many aldohexoses (for example, glucose, galactose, and mannose), and each can exist as alpha or beta anomers. Some aldohexoses can also form five-membered furanose rings under certain conditions.

Biological roles and occurrence: Glucose is the principal energy source for many organisms. Galactose and mannose are important components of glycoproteins, glycolipids, and polysaccharides. Aldohexoses serve as building blocks in carbohydrate biosynthesis and metabolism, and they appear in various forms in foods and in nature, either free or as constituents of larger carbohydrates such as starch, lactose, cellulose, and glycoproteins.

Industrial and analytical relevance: Aldohexoses are key standards in carbohydrate chemistry and are involved in metabolic pathways, enzymatic isomerizations, and several biotechnological applications.