Pentosaribosa

Pentosaribosa, or ribose, is a five-carbon aldose sugar (a pentose) that occurs in several stereoisomeric forms. In biochemistry it most commonly refers to D-ribose, the sugar component of RNA, which can adopt cyclic structures such as ribofuranose and, to a lesser extent, ribopyranose, with alpha and beta anomeric forms in solution.

In biology, pentosaribosa provides the backbone of nucleotides: ribose forms the core of ribonucleotides in RNA, and ribose-5-phosphate is a key intermediate produced by the pentose phosphate pathway for nucleotide synthesis and metabolic functions. The corresponding sugar in DNA is deoxyribose, lacking the 2'-hydroxyl group, which confers distinct chemical properties to DNA.

The term pentosaribosa covers the class of pentose sugars; other members include arabinose and xylose. The naturally occurring sugar is predominantly the D-enantiomer; L-ribose is rare in nature but can be synthesized and used in research.

Chemically, ribose is highly soluble in water and possesses an aldehyde group in its linear form, enabling various reactions such as glycosylation and phosphorylation to yield ribose-containing nucleotides. In biological systems, ribose is typically present in phosphorylated forms for energy and biosynthetic processes.