A nucleotide is composed of which components?

• A. A sugar and a base
• B. An amino acid and sugar
• C. A phosphate group, a 5-carbon sugar and a nitrogen-containing base.
• D. A phosphate group and a sugar but no base

Answer: (C)

Nucleotides are the building blocks of nucleic acids and consist of three parts: a five-carbon sugar (ribose in RNA or deoxyribose in DNA), a phosphate group, and a nitrogen-containing base. The sugar and phosphate form the backbone of DNA or RNA through phosphodiester bonds, while the base carries the genetic information by pairing with complementary bases. The base attaches to the sugar, linking all three essential components together.

That’s why the option describing a phosphate group, a five-carbon sugar, and a nitrogen-containing base is correct—both the sugar and the base without a phosphate, or a sugar plus phosphate without a base, or an unrelated molecule like an amino acid, don’t capture all three necessary pieces.