Structure
Ribose is an aldopentose (a monosaccharide containing five carbon atoms) that, in its open chain form, has an aldehyde functional group at one end. In the conventional numbering scheme for monosaccharides, the carbon atoms are numbered from C1' (in the aldehyde group) to C5'. The deoxyribose derivative found in DNA differs from ribose by having a hydrogen atom in place of the hydroxyl group at C2'.
Like many monosaccharides, ribose exists in an equilibrium among 5 forms--the linear form H−(C=O)−(CHOH)4–H and either of the two ring forms: alpha- or beta-ribofuranose ("C3'-endo"), with a five-membered ring, and alpha- or beta-ribopyranose ("C2'-endo"), with a six-membered ring. The beta-ribopyranose form predominates in aqueous solution.
The "-" in the name -ribose refers to the stereochemistry of the chiral carbon atom farthest away from the aldehyde group (C4'). In -ribose, as in all -sugars, this carbon atom has the same configuration as in -glyceraldehyde.
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