What is a nucleotide?

What is a nucleotide?

• A. A molecule that forms proteins
• B. The building block of DNA and RNA
• C. An enzyme that facilitates replication
• D. A type of lipid

Answer: (B)

Nucleotides are the basic units that make up DNA and RNA. Each nucleotide is built from a sugar (deoxyribose in DNA or ribose in RNA), a phosphate group, and a nitrogenous base (adenine, cytosine, guanine, and thymine in DNA or uracil in RNA). These units link together through phosphodiester bonds to form long polynucleotide chains, creating the backbone of the strands with the bases extending inward to encode genetic information. While nucleotides also serve roles like ATP as energy molecules or cAMP in signaling, their primary identity is that they are the building blocks of DNA and RNA. The other options refer to different biomolecule classes—proteins are made from amino acids, replication involves enzymes, and lipids are a separate type of molecule—so the description as the building blocks of DNA and RNA is the best fit.

Nucleotides are the basic units that make up DNA and RNA. Each nucleotide is built from a sugar (deoxyribose in DNA or ribose in RNA), a phosphate group, and a nitrogenous base (adenine, cytosine, guanine, and thymine in DNA or uracil in RNA). These units link together through phosphodiester bonds to form long polynucleotide chains, creating the backbone of the strands with the bases extending inward to encode genetic information. While nucleotides also serve roles like ATP as energy molecules or cAMP in signaling, their primary identity is that they are the building blocks of DNA and RNA. The other options refer to different biomolecule classes—proteins are made from amino acids, replication involves enzymes, and lipids are a separate type of molecule—so the description as the building blocks of DNA and RNA is the best fit.