Pentose
monosaccharide with five carbon atoms

In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. The chemical formula of many pentoses is C5H10O5, and their molecular weight is 150.13 g/mol.
Pentoses are very important in biochemistry. Ribose is a constituent of RNA, and the related molecule, deoxyribose, is a constituent of DNA. Phosphorylated pentoses are important products of the pentose phosphate pathway, most importantly ribose 5-phosphate (R5P), which is used in the synthesis of nucleotides and nucleic acids.
Like some other monosaccharides, pentoses exist in two forms, open-chain (linear) or closed-chain (cyclic), that easily convert into each other in water solutions. The linear form of a pentose, which usually exists only in solutions, has an open-chain backbone of five carbons. Four of these carbons have one hydroxyl functional group (–OH) each, connected by a single bond, and one has an oxygen atom connected by a double bond (=O), forming a carbonyl group (C=O). The remaining bonds of the carbon atoms are satisfied by six hydrogen atoms. Thus the structure of the linear form is H–(CHOH)x–C(=O)–(CHOH)4-x–H, where x is 0, 1, or 2.
The term "pentose" sometimes is assumed to include deoxypentoses, such as deoxyribose: compounds with general formula C5H10O5-y that can be described as derived from pentoses by replacement of one or more hydroxyl groups with hydrogen atoms.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jul 9, 2026. The linked authority identifier is Q205654. The Library of Congress control number is sh85099648. 1 of 1 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Pentose” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.