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In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. [1] The chemical formula of many pentoses is C 5 H 10 O 5, and their molecular weight is 150.13 g/mol. [2] Pentoses are very important in biochemistry. Ribose is a constituent of RNA, and the related molecule, deoxyribose, is a constituent of DNA.
L-Ribose Fischer Projection. Ribose is a simple sugar and carbohydrate with molecular formula C 5 H 10 O 5 and the linear-form composition H−(C=O)−(CHOH) 4 −H. The naturally occurring form, d-ribose, is a component of the ribonucleotides from which RNA is built, and so this compound is necessary for coding, decoding, regulation and expression of genes.
The general structure of a ribonucleotide consists of a phosphate group, a ribose sugar group, and a nucleobase, in which the nucleobase can either be adenine, guanine, cytosine, or uracil. Without the phosphate group, the composition of the nucleobase and sugar is known as a nucleoside.
Monosaccharides can be classified by the number x of carbon atoms they contain: triose (3), tetrose (4), pentose (5), hexose (6), heptose (7), and so on. Glucose, used as an energy source and for the synthesis of starch, glycogen and cellulose, is a hexose. Ribose and deoxyribose (in RNA and DNA, respectively) are pentose
Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group.A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups.
These prefixes are attached to the systematic name of the molecular graph. So for example, D-glucose is D-gluco-hexose, D-ribose is D-ribo-pentose, and D-psicose is D-ribo-hexulose. Note that, in this nomenclature, mirror-image isomers differ only in the ' D '/' L ' prefix, even though all their hydroxyls are reversed.
Because the phosphate group has two separate bonds to the ribose sugar, it forms a cyclic ring. [6] The atom numbering convention is used to identify the carbons and nitrogens within a cyclic nucleotide. In the pentose, the carbon closest to the carbonyl group is labeled C-1. When a pentose is connected to a nitrogenous base, carbon atom ...
Any of a class of enzymes which catalyze the decomposition of nucleosides into their component nitrogenous bases and pentose sugars. [12] nucleoside An organic molecule composed of a nitrogenous base bonded to a five-carbon sugar (either ribose or deoxyribose). A nucleotide additionally includes one or more phosphate groups. nucleosol