ribose, monosaccharide carbohydrate of universal distribution in living tissue, found in ribonucleic acid (RNA; see nucleic acid), free nucleotides, and various coenzymes. Its close relative, deoxyribose, is a constituent of deoxyribonucleic acid (DNA); ribose has one more oxygen atom in its molecule than deoxyribose. Some of the best procedures for the laboratory preparation of ribose involve the hydrolysis of yeast nucleic acid.

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.

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