nucleotide

enUK

nucleotide

(no͞o`klēətīd', nyo͞o`–), organic substance that serves as a monomer in forming nucleic acidsnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
..... Click the link for more information. . Nucleotides consist of either a purinepurine,
type of organic base found in the nucleotides and nucleic acids of plant and animal tissue. The German chemist Emil Fischer did much of the basic work on purines and introduced the term into the chemical literature in the early 20th cent.
..... Click the link for more information. or a pyrimidinepyrimidine
, type of organic base found in certain coenzymes and in the nucleic acids of plant and animal tissue. The three major pyrimidines of almost universal distribution in living systems are cytosine, thymine, and uracil.
..... Click the link for more information. base, a riboseribose
, monosaccharide carbohydrate of universal distribution in living tissue, found in ribonucleic acid (RNA; see nucleic acid), free nucleotides, and various coenzymes.
..... Click the link for more information. or deoxyribose, and a phosphate group. Adenosine triphosphateadenosine triphosphate
(ATP) , organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of
..... Click the link for more information. serves as the principle energy carrier for the cell's reactions. The most important nucleotides are those derived from the bases adenineadenine
, organic base of the purine family. Adenine combines with the sugar ribose to form adenosine, which in turn can be bonded with from one to three phosphoric acid units, yielding the three nucleotides adenosine monophosphate, adenosine diphosphate, and adenosine
..... Click the link for more information. , guanineguanine
, organic base of the purine family. It was reported (1846) to be in the guano of birds; later (1879–84) it was established as one of the major constituents of nucleic acids.
..... Click the link for more information. , cytosinecytosine
, organic base of the pyrimidine family. It was isolated from the nucleic acid of calf thymus tissue in 1894. A suggested structure for cytosine, published in 1903, was confirmed in the same year when that base was synthesized in the laboratory.
..... Click the link for more information. , thyminethymine
, organic base of the pyrimidine family. Thymine was the first pyrimidine to be purified from a natural source, having been isolated from calf thymus and beef spleen in 1893–4.
..... Click the link for more information. , and uraciluracil
, organic base of the pyrimidine family. It was isolated from herring sperm and also produced in a laboratory in 1900–1901. When combined with the sugar ribose in a glycosidic linkage, uracil forms a derivative called uridine (a nucleoside), which in turn can be
..... Click the link for more information. .

Nucleotide

A cellular constituent that is one of the building blocks of ribonucleic acids (RNA) and deoxyribonucleic acid (DNA). In biological systems, nucleotides are linked by enzymes in order to make long, chainlike polynucleotides of defined sequence. The order or sequence of the nucleotide units along a polynucleotide chain plays an important role in the storage and transfer of genetic information. Many nucleotides also perform other important functions in biological systems. Some, such as adenosine triphosphate (ATP), serve as energy sources that are used to fuel important biological reactions. Others, such as nicotinamide adenine dinucleotide (NAD) and coenzyme A (CoA), are important cofactors that are needed to complete a variety of enzymatic reactions. Cyclic nucleotides such as cyclic adenosine monophosphate (cAMP) are often used to regulate complex metabolic systems. Chemically modified nucleotides such as fluoro-deoxyridine monophosphate (Fl-dUMP) contain special chemical groups that are useful for inactivating the normal function of important enzymes. These and other such compounds are widely used as drugs and therapeutic agents to treat cancer and a variety of other serious illnesses. See Coenzyme, Cyclic nucleotides, Nicotinamide adenine dinucleotide (NAD)

Nucleotides are generally classified as either ribonucleotides or deoxyribonucleotides. Both classes consist of a phosphorylated pentose sugar that is linked via an N-glycosidic bond to a purine or pyrimidine base. The combination of the pentose sugar and the purine or pyrimidine base without the phosphate moiety is called a nucleoside. See Purine, Pyrimidine

Ribonucleosides contain the sugar d -ribose, whereas deoxyribonucleosides contain the sugar 2-deoxyribose. The four most common ribonucleosides are adenosine, guanosine, cytidine, and uridine. The purine ribonucleosides, adenosine and guanosine, contain the nitrogenous bases adenine and guanine, respectively. The pyrimidine ribonucleosides, cytidine and uridine, contain the bases cytosine and uracil, respectively. Similarly, the most common deoxyribonucleosides include deoxyadenosine, deoxyguanosine, deoxycytidine, and thymidine, which contains the pyrimidine base thymine. Phosphorylation of the ribonucleosides or deoxyribonucleosides yields the corresponding ribonucleotide or deoxyribonucleotide. See Deoxyribonucleic acid (DNA), Enzyme, Nucleic acid, Ribonucleic acid (RNA)

nucleotide

[′nü·klē·ə‚tīd] (biochemistry) An ester of a nucleoside and phosphoric acid; the structural unit of a nucleic acid.

nucleotide

enUK

nucleotide

[noo´kle-o-tīd] any of a group of compounds obtained by hydrolysis of nucleic acids, consisting of a purine or base" >pyrimidine base linked to a sugar (ribose or deoxyribose), which in turn is esterified with phosphoric acid.cyclic n's those in which the phosphate group bonds to two atoms of the sugar forming a ring, as in cyclic AMP and cyclic GMP, which act as intracellular second messengers.

nu·cle·o·tide

(nū'klē-ō-tīd), Originally a combination of a (nucleic acid) purine or pyrimidine, one sugar (usually ribose or deoxyribose), and a phosphoric group; by extension, any compound containing a heterocyclic compound bound to a phosphorylated sugar by an N-glycosyl link (for example, adenosine monophosphate, NAD⁺). For individual nucleotides see specific names. Synonym(s): mononucleotide

nucleotide

(no͞o′klē-ə-tīd′, nyo͞o′-)n. Any of a group of compounds consisting of a nucleoside combined with a phosphate group and constituting the units that make up DNA and RNA molecules.

nu·cle·o·tide

(nū'klē-ō-tīd) A combination of a (nucleic acid) purine or pyrimidine, one sugar (usually ribose or deoxyribose), and a phosphoric group.
Synonym(s): mononucleotide.

nucleotide

A molecule formed from the bonding of a purine or a pyrimidine base with a sugar and a mono-, di- or tri-phosphate group. Compare NUCLEOSIDE. Four different nucleotides may polymerize to form DNA. They are 2'-deoxyadenosine 5'-triphosphate; 2'-deoxyguanosine 5'-triphosphate; 2'-deoxycytidine 5'-triphosphate; and 2'-deoxythymidine 5'-triphosphate. These lengthy names are commonly abbreviated to dATP, dGTP, dCTP and dTTP. Even this is too clumsy when printing out the sequence of nucleotides in a length of DNA. In that case they are abbreviated to A, G, C and T (for adenine, guanine, cytosine and thymine). In RNA the sugar is not 2'-deoxyribose, but ribose itself. Also one of the RNA bases differs from that in DNA. Thymine is replaced by uracil. So the nucleotides of RNA are adenosine 5'-triphosphate; guanosine 5'-triphosphate; cytidine 5'-triphosphate; and uridine 5'-triphosphate. These are abbreviated to ATP, GTP, CTP and UTP or simply A, G, C and U.

Fig. 232 Nucleotide . Basic units of (a) deoxyribose sugar, (b) phosphate. Each carbon atom is numbered (1 prime, 2 prime, etc).

Fig. 233 Nucleotide . Linkage of the three nucleotide elements.

nucleotide

a complex organic molecule forming the basic unit of NUCLEIC ACIDS, with a structure made up of three components: a pentose sugar (ribose, or deoxyribose with one less oxygen atom), an organic base (PURINE type: ADENINE and GUANINE; or PYRIMIDINE type: CYTOSINE, THYMINE and URACIL) and a phosphate group (see Fig. 232 ). The three elements are linked together by two condensation reactions between the 1 sugar carbon and a base forming a NUCLEOSIDE, and the 5' sugar carbon and the phosphate (see Fig. 233 ). The nucleotides are formed into POLYNUCLEOTIDE CHAINS.

Nucleotide

Any of a group of organic molecules that link together to form the building blocks of DNA or RNA.Mentioned in: Myotonic Dystrophy

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Synonyms for nucleotide

noun a phosphoric ester of a nucleoside

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