In nucleic acid chemistry, compounds that contain an organic nitrogen-containing base, sugar, and phosphate group are called ___.

• A. Nucleosides
• B. Nucleotides
• C. Nucleic acids
• D. Bases

Answer: (B)

Nucleotides are the building blocks of nucleic acids, and each one contains three parts: a nitrogen-containing base, a five-carbon sugar, and a phosphate group. The presence of the phosphate is what makes this unit a nucleotide rather than just a nucleoside (which is base plus sugar without any phosphate). When nucleotides link together through phosphodiester bonds, they form the long polymers known as nucleic acids. The sugar can be deoxyribose in DNA or ribose in RNA, and the bases include purines and pyrimidines. ATP and similar molecules are also nucleotides, used for energy transfer, illustrating the versatile roles of these units. Therefore, the described compound is a nucleotide.