Nucleotide
A nucleotide is a chemical compound with three components: a nitrogen-containing base, a pentose (five-carbon) sugar, and one or more phosphate groups. Although best known as the structural units of the nucleic acids DNA and RNA, which encode genetic information in organisms, nucleotides participate in nearly all biochemical processes.
Nucleotides' role in metabolism:
- ATP, an adenine nucleotide, is a universal energy currency of energy in biological systems
- Adenine nucleotides are components of three major coenzymes, NAD plus, FAD, and CoA
- Nucleotides also serve as regulators of metabolism. Cyclic AMP is a ubiquitous mediator of the action of many hormones. Covalent modifications introduced by ATP alter the activities of many enzymes (e.g., phosphorylation of glycogen synthase)
Chemical structure and nomenclature
In the most common nucleotides, the base is a derivative of purine or pyrimidine, and the sugar is the pentose (five-carbon sugar) deoxyribose or ribose.
The base is a derivative of one of 2 (or 3?) heterocylic compounds (organic compounds that contain a ring structure with atoms in addition to carbon, such as sulfur, oxygen or nitrogen); the most common of which are:
- Purine (adenine and guanine)
- Pyrimidine (cytosime, thyme, and uracil)
- Pyridine (nicotinamide)
The sugar is a pentose (five-carbon sugar): either deoxyribose or ribose. “Deoxy” indicates that the sugar lacks an oxygen atom present in ribose, the parent compound. Depending on their base sugar, nucleotides are thus known as “deoxyribonucleotides” or “ribonucleotides.”
Nucleosides resemble the structure of nucleotides (i.e., they contain a purine or pyrmidine base bonded to a sugar) but lack the phosphate group (Stryer 76) Nucleotides are a phosphate ester of nucleotides. In chemistry, esters are organic compounds in which an organic group (symbolized by R' in this article) replaces a hydrogen atom (or more than one) in an oxygen acid.
Nucleotide names are abbreviated into standard three- or four-letter codes. The first letter is lower case and indicates whether the Nucleotide in question is a deoxyribonucleotide (denoted by a d) or a ribonucleotide (no letter). The second letter indicates the nucleoside corresponding to the nucleobase:
- G: Guanine
- A: Adenine
- T: Thymine
- C: Cytosine
- U: Uracil not present in DNA, but takes the place of Thymine in RNA
The third and fourth letters indicate the length of the attached phosphate chain (Mono-, Di-, Tri-) and the presence of a phosphate (P).
Thus, for example, deoxy-cytidine-triphosphate (pictured at right) is abbreviated as dCTP. (use more familiar nucleotide or explain function of dCTP)
Nucleotides encode genetic information
DNA is a polymer of deoxyribonucleotide units. Polymer is a term used to describe molecules consisting of structural units and a large number of repeating units connected by covalent chemical bonds.
In DNA, bases carry genetic information while sugar and phosphate groups provide a structural role (as the base is the variable part).
Structure of DNA: two helical polynucleotide chains are coiled around a common axis. The chains run in opposite directions. The bases are on the inside of the helix, while the sugar-phosphate backbone is on the outside. The two chains are held together by hydrogen bonds between pairs of bases. Adenine is always paired with thymine; guanine with cytosine (i.e., a purine to a pyrimidine).
Two differences of RNA, which can serve as genetic material in viruses: (1) sugar units are riboses rather than deoxyriboses and (2) one of the four major bases is uracil (U) instead of thymine (T); can be single or double-stranded
RNA molecules can contain as few as 75 nucleotides to more than 5000 nucleotides.
The genetic code is the relation between the sequence of bases in DNA (or its RNA transcript) and the sequence of amino acids in proteins. Amino acids are coded by groups of three bases (called codons) starting from a fixed point.
Nucleotides function in cell metabolism
ATP is the universal energy currency of the cell
Several nucleotides function as coenzymes
Nucleotides also play a role in regulation of metabolism
Chemical structures
Nucleotides
 Adenosine monophosphate AMP |
 Adenosine diphosphate ADP |
Adenosine triphosphate ATP |
 Guanosine monophosphate GMP |
 Guanosine diphosphate GDP |
 Guanosine triphosphate GTP |
 Thymidine monophosphate TMP |
 Thymidine diphosphate TDP |
 Thymidine triphosphate TTP |
 Uridine monophosphate UMP |
 Uridine diphosphate UDP |
 Uridine triphosphate UTP |
 Cytidine monophosphate CMP |
 Cytidine diphosphate CDP |
 Cytidine triphosphate CTP |
Deoxynucleotides
 Deoxyadenosine monophosphate dAMP |
 Deoxyadenosine diphosphate dADP |
 Deoxyadenosine triphosphate dATP |
 Deoxyguanosine monophosphate dGMP |
 Deoxyguanosine diphosphate dGDP |
 Deoxyguanosine triphosphate dGTP |
 Deoxythymidine monophosphate dTMP |
 Deoxythymidine diphosphate dTDP |
 Deoxythymidine triphosphate dTTP |
 Deoxyuridine monophosphate dUMP |
 Deoxyuridine diphosphate dUDP |
 Deoxyuridine triphosphate dUTP |
 Deoxycytidine monophosphate dCMP |
 Deoxycytidine diphosphate dCDP |
 Deoxycytidine triphosphate dCTP |
| Code | Equivalence | Complement |
|---|---|---|
| A | A | T or U |
| C | C | G |
| G | G | C |
| T or U | T | A |
| M | A or C | K |
| R | A or G | Y |
| W | A or T | W |
| S | C or G | S |
| Y | C or T | R |
| K | G or T | M |
| V | A or C or G | B |
| H | A or C or T | D |
| D | A or G or T | H |
| B | C or G or T | V |
| X or N | A or C or G or T | X |
ReferencesISBN links support NWE through referral fees
- Stryer, Lubert. 1995. Biochemistry, 4th edition. New York, NY: W.H. Freeman.
External links
- Abbreviations and Symbols for Nucleic Acids, Polynucleotides and their Constituents (IUPAC)
- Provisional Recommendations 2004 (IUPAC)
| Nucleic acids edit |
|---|
| Nucleobases: Adenine - Thymine - Uracil - Guanine - Cytosine - Purine - Pyrimidine |
| Nucleosides: Adenosine - Uridine - Guanosine - Cytidine - Deoxyadenosine - Thymidine - Deoxyguanosine - Deoxycytidine |
| Nucleotides: AMP - UMP - GMP - CMP - ADP - UDP - GDP - CDP - ATP - UTP - GTP - CTP - cAMP - cGMP |
| Deoxynucleotides: dAMP - dTMP - dUMP - dGMP - dCMP - dADP - dTDP - dUDP - dGDP - dCDP - dATP - dTTP - dUTP - dGTP - dCTP |
| Nucleic acids: DNA - RNA - LNA - PNA - mRNA - ncRNA - miRNA - rRNA - siRNA - tRNA - mtDNA - Oligonucleotide |
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