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Any of a class of organic compounds, including the structural units of nucleic acids. Each consists of a nucleoside and one or more phosphate groups. In nucleic acids, the phosphate of one nucleotide joins to the sugar of the next to form the backbone. Important nucleotides that are not part of nucleic acids include ATP, cyclic AMP (needed in glycogen breakdown), and certain coenzymes.
This entry comes from Encyclopædia Britannica Concise. For the full entry on nucleotide, visit Britannica.com.