Which components make up a nucleotide?

• A. Phosphate group, pentose sugar, nitrogenous bases
• B. Amino acids, ribose, phosphate
• C. Nitrogen gas, water, carbon
• D. Deoxyribose, lipids, phosphate

Answer: (A)

Nucleotides are the basic units of nucleic acids, and each one is made of three parts: a phosphate group, a five-carbon sugar, and a nitrogenous base. The sugar is a pentose, either ribose in RNA or deoxyribose in DNA, and the phosphate group bonds with the sugar to form the backbone while the base carries the genetic information. The nitrogenous base is what provides the sequence that encodes genes. That combination—phosphate group, pentose sugar, and nitrogenous bases—is exactly what defines a nucleotide. Other options mix in components from proteins or lipids or list elemental substances, which aren’t part of a nucleotide.