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2.13:_Nucleotides
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<p class="lt-bio-3791" style="background-color: unset;"><strong>Nucleic acids</strong> are linear, unbranched polymers of <strong>nucleotides</strong>. Nucleotides consist of three parts.</p> <p class="mt-align-center lt-bio-3791" style="background-color: unset;"><img class="internal" alt="Nucleotide structure: pentose sugar with phosphate on 5' carbon, base site on 1', and H (DNA) or OH (RNA) on 2'." loading="lazy" src="https://bio.libretexts.org/@api/deki/files/5159/Pentose.gif?revision=1" aria-describedby="remedy-description-0df40285464e6862" /><span id="remedy-description-0df40285464e6862" data-remedy-image-description="0df40285464e6862" style="display: block; white-space: pre-line;">Diagram of a nucleotide's components. At left, a phosphate group: a central P double-bonded to O below, single-bonded to two O??? groups (above and left), and linked through an O to the CH??? of the 5' carbon. The CH??? connects to C4' (bearing an H), which closes a five-membered sugar ring through a ring oxygen at top. Ring carbons are labeled 5', C4', C3', C2', and C1'. C3' carries an H and an OH. C2' carries an H; below it two circled groups with arrows indicate the alternative substituent at this position: a circled H labeled 'in deoxyribonucleotides' and a circled OH labeled 'in ribonucleotides', with a double-headed arrow linking the two circles. C1', at the right of the ring, bears an H, and an arrow points to it from a boxed label reading 'to base (purine or pyrimidine)', showing where the nucleobase attaches. The figure thus contrasts deoxyribose (H at 2') and ribose (OH at 2') within an otherwise identical nucleotide framework.</span></p> <p class="lt-bio-3791" style="background-color: unset;">A five-carbon sugar (hence a <strong>pentose</strong>). Two kinds are found:</p> <ul> <li class="lt-bio-3791" style="background-color: unset;"><strong>deoxyribose</strong>, which has a hydrogen atom attached to its #2 carbon atom (designated 2'), and</li> <li class="lt-bio-3791" style="background-color: unset;"><strong>ribose</strong>, which has a hydroxyl group there.</li> </ul> <p class="lt-bio-3791" style="background-color: unset;">Deoxyribose-containing nucleotides, the <strong>deoxyribonucleotides</strong>, are the monomers of deoxyribonucleic acids (<strong>DNA)</strong>. Ribose-containing nucleotides, the <strong>ribonucleotides</strong>, are the monomers of ribonucleic acids (<strong>RNA)</strong>.</p> <p style="margin-left: 120px; background-color: unset;" class="lt-bio-3791"><img style="width: 164px; height: 278px;" class="internal" alt="Adenine and guanine structures, with their sugar-attachment sites marked." loading="lazy" width="164px" height="278px" src="https://bio.libretexts.org/@api/deki/files/5160/Purines.gif?revision=1&size=bestfit&width=164&height=278" aria-describedby="remedy-description-c5c28bb8d6b656eb" /><span id="remedy-description-c5c28bb8d6b656eb" data-remedy-image-description="c5c28bb8d6b656eb" style="display: block; white-space: pre-line;">Each purine has a six-membered ring fused to a five-membered ring. Adenine has an NH2 group above the six-membered ring. Guanine has a carbonyl oxygen above that ring and an NH2 group at its lower left. A red arrow from the nitrogen at the bottom of each five-membered ring marks attachment to the 1??? carbon of either pentose sugar.</span> <img style="width: 141px; height: 440px;" class="internal" alt="Ring structures of the pyrimidines thymine, cytosine, and uracil, each with an arrow showing attachment to a sugar's 1' carbon." loading="lazy" width="141px" height="440px" src="https://bio.libretexts.org/@api/deki/files/5161/Pyrimidines.gif?revision=1&size=bestfit&width=141&height=440" aria-describedby="remedy-description-9e7cd9883e45b619" /><span id="remedy-description-9e7cd9883e45b619" data-remedy-image-description="9e7cd9883e45b619" style="display: block; white-space: pre-line;">The image shows the chemical ring structures of the three pyrimidine nucleobases, drawn as six-membered rings with blue atom labels and names in blue text. (1) Thymine (T): the ring has a carbonyl (C=O) at the top, an HN at the upper left, a second carbonyl (O=C) at the lower left, and an N at the bottom; the right side bears a CH and a carbon carrying a methyl group (CH3). A red arrow points downward from the bottom nitrogen with the label 'to 1' carbon of deoxyribose.' (2) Cytosine (C): the ring has a carbon bearing an amino group (NH2) at the top, an N at the upper left, a carbonyl (O=C) at the lower left, and an N at the bottom; the right side has two CH groups. A red arrow points downward labeled 'to 1' carbon of either pentose.' (3) Uracil (U): the ring has a carbonyl (C=O) at the top, an HN at the upper left, a carbonyl (O=C) at the lower left, and an N at the bottom; the right side has two CH groups. A red arrow points downward labeled 'to 1' carbon of ribose.' The arrows indicate where each base bonds to its sugar: thymine to deoxyribose (DNA), uracil to ribose (RNA), and cytosine to either sugar.</span></p> <p style="margin-left: 160px; background-color: unset;" class="lt-bio-3791"><em>The Purines The Pyrimidines</em></p> <p class="lt-bio-3791" style="background-color: unset;">A nitrogen-containing ring structure called a <strong>nucleobase</strong> (or simply a base). The nucleobase is attached to the 1' carbon atom of the pentose. In <strong>DNA</strong>, four different nucleobases are found:</p> <ul> <li class="lt-bio-3791" style="background-color: unset;">two<strong> purines</strong>, called <strong>adenine</strong> (<strong>A</strong>) and <strong>guanine</strong> (<strong>G</strong>)</li> <li class="lt-bio-3791" style="background-color: unset;">two <strong>pyrimidines</strong>, called <strong>thymine</strong> (<strong>T</strong>) and <strong>cytosine</strong> (<strong>C</strong>)</li> </ul> <p class="lt-bio-3791" style="background-color: unset;"><strong>RNA</strong> contains:</p> <ul> <li class="lt-bio-3791" style="background-color: unset;">The same purines, <strong>adenine</strong> (<strong>A</strong>) and <strong>guanine</strong> (<strong>G</strong>).</li> <li class="lt-bio-3791" style="background-color: unset;">RNA also uses the pyrimidine <strong>cytosine</strong> (<strong>C</strong>), but instead of thymine, it uses the pyrimidine <strong>uracil</strong> (<strong>U</strong>).</li> </ul> <span id="Nucleoside"></span><span id="Nucleoside-2"></span><h2 style="background-color: unset;" class="lt-bio-3791">Nucleoside</h2> <p class="lt-bio-3791" style="background-color: unset;">The combination of a nucleobase and a pentose is called a <strong>nucleoside</strong>.</p> <p style="margin-left: 160px; background-color: unset;" class="lt-bio-3791"><img style="width: 419px; height: 354px;" class="internal" alt="Diagram of DNA elongation: a 3???-OH reacts with a deoxyribonucleoside triphosphate, releasing pyrophosphate." loading="lazy" width="419px" height="354px" src="https://bio.libretexts.org/@api/deki/files/5164/DNAsynthesis5eL3.png?revision=1&size=bestfit&width=419&height=354" aria-describedby="remedy-description-3065983e1eccf535" /><span id="remedy-description-3065983e1eccf535" data-remedy-image-description="3065983e1eccf535" style="display: block; white-space: pre-line;">The diagram shows a vertical DNA strand on the left, with its lower terminus labeled ???3??? end of DNA strand??? and bearing a 3??? hydroxyl group. Below it is an incoming ???Deoxyribonucleoside triphosphate,??? consisting of a pentose sugar with a generic ???Base,??? H at the 2??? carbon, and three phosphates attached at the 5??? carbon. A reaction arrow points right to an extended DNA strand in which the incoming nucleotide is connected at the former 3??? end by a new phosphodiester bond. The other product is labeled ???Pyrophosphate (PPi)??? and is drawn as two linked phosphate groups. Sugar positions 2???, 3???, and 5???, along with H and OH groups and phosphate oxygens, are marked.</span></p> <p class="lt-bio-3791" style="background-color: unset;">One (as shown in the first figure), two, or three <strong>phosphate</strong> groups. These are attached to the 5' carbon atom of the pentose. The product in each case is called a <strong>nucleotide</strong>. Both DNA and RNA are assembled from <strong>nucleoside triphosphates</strong>.</p> <ul> <li class="lt-bio-3791" style="background-color: unset;">For <strong>DNA</strong>, these are <strong>dATP</strong>, <strong>dGTP</strong>, <strong>dCTP</strong>, and <strong>dTTP</strong>.</li> <li class="lt-bio-3791" style="background-color: unset;">For <strong>RNA</strong>, these are <strong>ATP</strong>, <strong>GTP</strong>, <strong>CTP</strong>, and <strong>UTP</strong>.</li> </ul> <p class="lt-bio-3791" style="background-color: unset;">In both cases, as each nucleotide is attached, the second and third phosphates are removed.</p> <table class="mt-responsive-table" align="center" border="1"> <caption>Table 2.13.1: The nucleosides and their mono-, di-, and triphosphates</caption> <thead><tr> <th scope="col" id="th-nucleic-acid">Nucleic acid</th> <th scope="col" id="th-nucleobase">Nucleobase</th> <th scope="col" id="th-nucleoside">Nucleoside</th> <th colspan="3" scope="colgroup" id="th-nucleotides">Nucleotides</th> </tr></thead><tbody> <tr> <th rowspan="4" scope="rowgroup" id="th-dna">DNA</th> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-dna">Adenine (A)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-dna">Deoxyadenosine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dAMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dADP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dATP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-dna">Guanine (G)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-dna">Deoxyguanosine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dGMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dGDP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dGTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-dna">Cytosine (C)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-dna">Deoxycytidine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dCMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dCDP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dCTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-dna">Thymine (T)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-dna">Deoxythymidine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dTMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dTDP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-dna">dTTP</td> </tr> <tr> <th rowspan="4" scope="rowgroup" id="th-rna">RNA</th> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-rna">Adenine (A)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-rna">Adenosine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">AMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">ADP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">ATP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-rna">Guanine (G)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-rna">Guanosine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">GMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">GDP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">GTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-rna">Cytosine (C)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-rna">Cytidine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">CMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">CDP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">CTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleobase th-rna">Uracil (U)</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleoside th-rna">Uridine</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">UMP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">UDP</td> <td class="lt-bio-3791" style="background-color: unset;" headers="th-nucleotides th-rna">UTP</td> </tr> </tbody> </table> <footer class="mt-content-footer"> <style>/*<![CDATA[*/#mt-toc-container {display: none !important;}/*]]>*/</style><script type="text/javascript">/*<![CDATA[*/ $(function() { if(!window['autoDefinitionList']){ window['autoDefinitionList'] = true; $('dl').find('dt').on('click', function() { $(this).next().toggle('350'); }); } });/*]]>*/</script> <script defer="true" src="https://static.cloudflareinsights.com/beacon.min.js" data-cf-beacon="{"token": "483ec2414e274209a7e93c253192df0b"}"></script><script src="https://cdn.libretexts.net/github/LibreTextsMain/Miscellaneous/h5p-resizer.js"></script><script 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