C5ribose

C5ribose is the five-carbon aldose known in biology as ribose, the sugar component of ribonucleic acid. Its molecular formula is C5H10O5, and in living systems the D-enantiomer is the biologically relevant form. In solution, ribose exists in both open-chain and cyclic forms, with the cyclic five-membered ribofuranose ring being the predominant structure; alpha and beta anomers can form at the anomeric carbon.

In RNA, ribose forms the sugar-phosphate backbone, linking with phosphate groups and nitrogenous bases to create nucleotides such as adenosine, cytidine, guanosine, and uridine. The presence of a hydroxyl group at the 2′ position distinguishes ribose from deoxyribose, the sugar of DNA, which lacks that 2′-hydroxyl. Ribose can also be found in its phosphorylated forms, notably ribose-5-phosphate, a key intermediate in nucleotide biosynthesis and the pentose phosphate pathway.

Biological roles and metabolism: ribose is synthesized internally primarily through the pentose phosphate pathway to supply ribose-5-phosphate for nucleotide and cofactor production. It can be salvaged or converted into other pentose sugars as needed by the cell. Dietary ribose is generally metabolized through normal carbohydrate pathways and does not accumulate in large amounts.

Physical and chemical properties: ribose is water-soluble and behaves as a reducing sugar due to its open-chain aldehyde form. It readily participates in glycosidic bond formation to give nucleosides and nucleotides and can interconvert between its various anomeric and ring forms in aqueous environments.

C5ribose is essential for RNA structure and function and plays a central role in cellular metabolism and nucleotide biosynthesis.