Nucleotide

Lore & Background

Nucleotides are composed of three distinctive chemical sub-units: a five-carbon sugar molecule, a nucleobase (together called a nucleoside), and one phosphate group. With all three joined, a nucleotide is also termed a nucleoside monophosphate, diphosphate, or triphosphate depending on the number of phosphates. In nucleic acids, nucleotides contain either a purine or a pyrimidine base, and are termed ribonucleotides if the sugar is ribose, or deoxyribonucleotides if the sugar is deoxyribose. Individual phosphate molecules repetitively connect the sugar-ring molecules in adjacent nucleotide monomers, creating a backbone strand for a single- or double helix. In a double helix, the two strands are oriented in opposite directions, permitting base pairing and complementarity essential for replicating or transcribing encoded information.

Reader's Guide

Nucleotides are fundamental to all life on Earth as the building blocks of DNA and RNA, the molecules that store and transmit genetic information. Beyond their structural role, they are central to cellular metabolism, providing chemical energy in the form of nucleoside triphosphates such as ATP, GTP, CTP, and UTP. They also participate in cell signaling through cyclic nucleotides like cGMP and cAMP, and are incorporated into important enzymatic cofactors including coenzyme A, FAD, FMN, NAD, and NADP+. In experimental biochemistry, nucleotides can be radiolabeled to yield radionucleotides. Additionally, 5-nucleotides are used as flavor enhancers to enhance umami taste, often in the form of yeast extract. The synthesis of nucleotides occurs both de novo and through salvage pathways, with the liver being the major organ for de novo synthesis. Pyrimidine and purine nucleotides are synthesized via distinct pathways in the cytoplasm, involving multiple enzymatic steps.

Did You Know?

• Nucleotides are composed of a nucleobase, a five-carbon sugar (ribose or deoxyribose), and a phosphate group.
• The four nucleobases in DNA are guanine, adenine, cytosine, and thymine; in RNA, uracil replaces thymine.
• Nucleotides provide chemical energy in the form of ATP, GTP, CTP, and UTP.
• 5-nucleotides are used as flavor enhancers to enhance umami taste, often in yeast extract.