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Nucleic acids are biological polymers consisting of DNA and RNA, polymers that consist of nucleotide residues. A nucleotide is formed from three chemical components: a phosphate group, a monosaccharide residue (either ribose or deoxyribose), and an organic base. The phosphoester bonding pattern occurs when a monosaccharide bonds with the phosphate group, and an N-glycosidic bond is made when the monosaccharide bonds to a nitrogen in the organic base. Deoxyribonucleotides make up DNA and contain a deoxyribose residue, a phosphate residue, and adenine, guanine, cytosine, or thymine organic bases. Ribonucleotides make up RNA and contain a ribose residue, a phosphate residue, and adenine, guanine, cytosine, or uracil organic bases. Nucleotides have biological roles other than forming DNA and RNA, including energy-transfer molecules like ATP and ADP, and cyclic nucleotides act as signaling compounds. A polynucleotide is a polymer made from nucleotide residues, and a chain of covalently bonded nucleotides is referred to as a polynucleotide, with nucleotides covalently bonded to each other by a phosphodiester bonding pattern between a 3’ carbon on one monosaccharide and 5’ carbon on the other monosaccharide.