pentoser

Pentoser is the term used for pentoses, monosaccharides with five carbon atoms. They share the general formula C5H10O5 and occur as aldopentoses, in which the aldehyde group is at carbon 1, and ketopentoses, with the carbonyl on carbon 2. They are chiral and exist as enantiomeric pairs; in biology the D-forms are predominant.

Common aldopentoses are ribose, arabinose, and xylose, as well as 2-deoxyribose, a deoxygenated form of ribose that forms the sugar backbone of DNA. Ketopentoses include ribulose and xylulose.

Biological significance: ribose is a constituent of RNA, ATP, and many cofactors; deoxyribose forms the backbone of DNA. Ribose-5-phosphate is produced in the pentose phosphate pathway, which also generates NADPH and provides ribose-5-phosphate for nucleotide synthesis.

Pentoses also occur in plant cell walls as components of hemicelluloses, and certain microorganisms metabolize xylose and arabinose. In metabolism, pentoses can be rearranged through the non-oxidative phase of the pentose phosphate pathway to yield glyceraldehyde-3-phosphate and fructose-6-phosphate, feeding into glycolysis or energy production.

Industrial and research relevance: pentoses are studied in biochemistry, nutrition, and biofuels because of their roles in nucleic acids and biomass derived from plant material.