Nucleotidesugar

Nucleotidesugar refers to the pentose sugar component of nucleotides, the sugar moiety that forms the backbone of nucleic acids. In nucleotides, the sugar is either ribose in RNA or deoxyribose in DNA. The sugars are five‑carbon furanose rings, and in nucleotides the preferred stereochemistry is the beta-D configuration. The sugar is linked to a nucleobase via a β-N-glycosidic bond at the 1' position to yield a nucleoside (for example, adenosine, cytidine). When one or more phosphate groups are attached to the 5' carbon, the molecule becomes a nucleotide.

Ribose carries a hydroxyl group at the 2' position (2'-OH), whereas deoxyribose lacks this hydroxyl (2'-H). This difference underpins the distinct chemical properties of RNA and DNA; the 2'-OH in ribose makes RNA more prone to hydrolysis and influences the conformational preferences (C3'-endo in RNA, C2'-endo in many DNA forms). The sugar also constrains the sugar-phosphate backbone geometry, with alternating 3' to 5' phosphodiester linkages during polymerization.

Role and significance: The nucleosugar provides the scaffold for nucleic acids and defines the chemistry of the sugar-phosphate backbone. The phosphate groups connect sugar units to form nucleic acids, while the attached base determines genetic information and recognition properties. In metabolism, ribose metabolism and ribonucleotide synthesis supply RNA precursors, while ribonucleotide reductase converts ribose-containing precursors into 2'-deoxyribose for DNA synthesis. Modified sugars or sugar analogs are used in research and therapy, illustrating the versatility of the nucleotidesugar framework.