Which statement correctly distinguishes a nucleoside from a nucleotide?

Which statement correctly distinguishes a nucleoside from a nucleotide?

• A. A nucleoside has three phosphates, while a nucleotide has one phosphate.
• B. A nucleoside includes phosphate groups, while a nucleotide does not.
• C. Nucleosides are built from sugars only; nucleotides include bases.
• D. Nucleosides are components of DNA backbone; nucleotides are temporary carriers of information.

Answer: (A)

The important idea is whether phosphate groups are present. A nucleoside is just a sugar (ribose or deoxyribose) bonded to a nitrogenous base and has no phosphate groups. A nucleotide starts from that same sugar-base unit but adds one or more phosphate groups, so it includes phosphate(s) in addition to the sugar and base. This distinction matters for how nucleic acids are built. DNA and RNA strands are made from nucleotides linked by phosphodiester bonds, forming a sugar–phosphate backbone. Nucleosides themselves don’t form this backbone; they are precursors or breakdown products. In cells, nucleotides can carry different numbers of phosphates (monophosphate, diphosphate, or triphosphate), and the high-energy triphosphates (like ATP, GTP) also supply energy for polymerization.

The important idea is whether phosphate groups are present. A nucleoside is just a sugar (ribose or deoxyribose) bonded to a nitrogenous base and has no phosphate groups. A nucleotide starts from that same sugar-base unit but adds one or more phosphate groups, so it includes phosphate(s) in addition to the sugar and base.

This distinction matters for how nucleic acids are built. DNA and RNA strands are made from nucleotides linked by phosphodiester bonds, forming a sugar–phosphate backbone. Nucleosides themselves don’t form this backbone; they are precursors or breakdown products. In cells, nucleotides can carry different numbers of phosphates (monophosphate, diphosphate, or triphosphate), and the high-energy triphosphates (like ATP, GTP) also supply energy for polymerization.