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What are nucleotides made of?

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Diagram of a DNA polynucleotide chain showing linked deoxyribose sugars, phosphate groups, and nitrogenous bases (adenine, guanine, cytosine, thymine), with an inset comparing ribose and uracil in RNA. — Nucleic acid A portion of the polynucleotide chain of deoxyribonucleic acid (DNA), with an inset showing the corresponding pentose sugar and pyrimidine base in ribonucleic acid (RNA).

Nucleotides are the fundamental building blocks of nucleic acids, such as DNA and RNA. Each nucleotide is composed of three distinct chemical components:12

A nitrogen-containing base: These are derivatives of purine, pyrimidine, or pyridine. The primary bases found in nucleic acids include adenine, guanine, cytosine, thymine, and uracil.12
A pentose sugar: A five-carbon sugar molecule. In DNA, this is deoxyribose, while in RNA, it is ribose.13
A phosphate group: This group links the sugar residues together to form the backbone of the nucleic acid chain.12

When a sugar is attached to a base but lacks the phosphate group, the molecule is referred to as a nucleoside.12