ribose

Ribose is a five-carbon aldose (aldopentose) with the chemical formula C5H10O5. In biological systems it is principally the D-enantiomer, though L-ribose exists in some organisms and synthetic contexts.

In solution ribose exists mainly in cyclic forms; the preferred ring is ribofuranose, a five-membered ring. The ring can be in alpha or beta configuration at the anomeric carbon and can interconvert with the open-chain form.

Ribose plays a central role in biology as the sugar component of RNA, where each nucleotide is linked through ribose-phosphate backbones to form the RNA polymer. It is also a part of many cofactors and nucleotides, including ATP, NAD+, and FAD. The sugar also appears in ribose-5-phosphate, a key intermediate of the pentose phosphate pathway, which feeds nucleotide synthesis and other biosynthetic processes.

In DNA the sugar is 2'-deoxyribose, which lacks an oxygen atom at the 2' position; this difference influences the chemical properties and stability of DNA and RNA.

Ribose is highly polar and water-soluble. It is a reducing sugar and occurs naturally in RNA and as a metabolically produced intermediate. Dietary D-ribose is available as a supplement, though its physiological benefits are a subject of study.