Nucleic Acids

Nucleotide

This nucleotide contains the five-carbon sugardeoxyribose, a nitrogenous base calledadenine, and one phosphate group. Together, the deoxyribose and adenine make up anucleoside (specifically, adeoxyribonucleoside) called deoxyadenosine. With the one phosphate group included, whole structure is considered a deoxyribonucleotide(a nucleotide constituent of DNA) with the name deoxyadenosine monophosphate.

Nucleotides are organic molecules that serve as the monomers, or subunits, of nucleic acids like DNA and RNA. The building blocks of nucleic acids, nucleotides are composed of a nitrogenous base, a five-carbon sugar(ribose or deoxyribose), and at least onephosphate group.

Nucleotides serve to carry packets of energy within the cell (ATP). In the form of thenucleoside triphosphates (ATP, GTP, CTP andUTP), nucleotides play central roles inmetabolism.[1] In addition, nucleotides participate in cell signaling (cGMP andcAMP), and are incorporated into importantcofactors of enzymatic reactions (e.g.coenzyme A, FAD, FMN, NAD, and NADP+).

Structure

The structure of nucleotide monomers.

A nucleotide is composed of a nucleobase(also termed a nitrogenous base), a five-carbon sugar (either ribose or 2-deoxyribose), and one or, depending on the definition, more than one phosphate groups. Authoritative chemistry sources such as the ACS Style Guide[2] and IUPAC Gold Book[3] clearly state that the term nucleotide refers only to a molecule containing one phosphate. However, common usage in molecular biology textbooks often extends this definition to include molecules with two or three phosphate groups.[1][4][5][6] Thus, the term "nucleotide" generally refers to a nucleoside monophosphate, but a nucleoside diphosphate or nucleoside triphosphate could be considered a nucleotide as well.

Without the phosphate group, the nucleobase and sugar compose a nucleoside. The phosphate groups form bonds with either the 2, 3, or 5-carbon of the sugar, with the 5-carbon site most common. Cyclic nucleotidesform when the phosphate group is bound to two of the sugar's hydroxyl groups.[1]Nucleotides contain either a purine or apyrimidine base. Ribonucleotides are nucleotides in which the sugar is ribose.Deoxyribonucleotides are nucleotides in which the sugar is deoxyribose.

Nucleic acids are polymeric macromolecules made from nucleotide monomers. In DNA, the purine bases are adenine and guanine, while the pyrimidines are thymine and cytosine. RNA uses uracil in place of thymine. Adenine always pairs with thymine by 2 hydrogen bonds, while guanine pairs with cytosine through 3 hydrogen bonds, each due to their unique structures.

Structural elements of common nucleic acid constituents. Because they contain at least one phosphate group, the compounds marked nucleoside monophosphate, nucleoside diphosphate and nucleoside triphosphate are all nucleotides (not simply phosphate-lacking nucleosides).