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.