: a pentose C5H10O5 found especially in the levorotatory D-form as a constituent of a number of nucleosides (as adenosine, cytidine, and guanosine) especially in RNA
Five-carbon sugar found in RNA. (In DNA the corresponding sugar is the closely related deoxyribose.) A ribose molecule combined with adenine, guanine, cytosine, or uracil forms a nucleoside; adding a phosphate group forms a nucleotide. The ribose of one nucleotide joins with the phosphate of the next to form the RNA backbone. Ribose phosphates are components of various coenzymes and are used by microorganisms in synthesizing histidine.