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="Diagram showing molecular structures of deoxyribonucleotides and ribonucleotides, highlighting differences at the 2 carbon position: deoxyribose (H) vs ribose (OH), and linkage to bases." loading="lazy" src="https://bio.libretexts.org/@api/deki/files/5159/Pentose.gif?revision=1" /></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="Chemical structures of adenine (A) and guanine (G) with labeled nitrogen atoms. Arrows point to NH groups, indicating the 1 attachment point for ribose sugars in nucleotide formation." loading="lazy" width="164px" height="278px" src="https://bio.libretexts.org/@api/deki/files/5160/Purines.gif?revision=1&amp;size=bestfit&amp;width=164&amp;height=278" />                                    <img style="width: 141px; height: 440px;" class="internal" alt="Diagram showing three chemical reactions labeled A, B, and C, displaying molecular structures with red and black text for descriptions and blue labels on molecular parts." loading="lazy" width="141px" height="440px" src="https://bio.libretexts.org/@api/deki/files/5161/Pyrimidines.gif?revision=1&amp;size=bestfit&amp;width=141&amp;height=440" /></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"></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 RNA synthesis: a chain of nucleotide structures linked together, indicating the 3 and 5 ends. Labels show base, ribose, and phosphate groups with arrows indicating process direction." loading="lazy" width="419px" height="354px" src="https://bio.libretexts.org/@api/deki/files/5164/DNAsynthesis5eL3.png?revision=1&amp;size=bestfit&amp;width=419&amp;height=354" /></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> <tbody> <tr> <th> </th> <th>Nucleobase</th> <th>Nucleoside</th> <th colspan="3">Nucleotides</th> </tr> <tr> <th rowspan="4">DNA</th> <td class="lt-bio-3791" style="background-color: unset;">Adenine (A)</td> <td class="lt-bio-3791" style="background-color: unset;">Deoxyadenosine</td> <td class="lt-bio-3791" style="background-color: unset;">dAMP</td> <td class="lt-bio-3791" style="background-color: unset;">dADP</td> <td class="lt-bio-3791" style="background-color: unset;">dATP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;">Guanine (G)</td> <td class="lt-bio-3791" style="background-color: unset;">Deoxyguanosine</td> <td class="lt-bio-3791" style="background-color: unset;">dGMP</td> <td class="lt-bio-3791" style="background-color: unset;">dGDP</td> <td class="lt-bio-3791" style="background-color: unset;">dGTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;">Cytosine (C)</td> <td class="lt-bio-3791" style="background-color: unset;">Deoxycytidine</td> <td class="lt-bio-3791" style="background-color: unset;">dCMP</td> <td class="lt-bio-3791" style="background-color: unset;">dCDP</td> <td class="lt-bio-3791" style="background-color: unset;">dCTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;">Thymine (T)</td> <td class="lt-bio-3791" style="background-color: unset;">Deoxythymidine</td> <td class="lt-bio-3791" style="background-color: unset;">dTMP</td> <td class="lt-bio-3791" style="background-color: unset;">dTDP</td> <td class="lt-bio-3791" style="background-color: unset;">dTTP</td> </tr> <tr> <th rowspan="4">RNA</th> <td class="lt-bio-3791" style="background-color: unset;">Adenine (A)</td> <td class="lt-bio-3791" style="background-color: unset;">Adenosine</td> <td class="lt-bio-3791" style="background-color: unset;">AMP</td> <td class="lt-bio-3791" style="background-color: unset;">ADP</td> <td class="lt-bio-3791" style="background-color: unset;">ATP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;">Guanine (G)</td> <td class="lt-bio-3791" style="background-color: unset;">Guanosine</td> <td class="lt-bio-3791" style="background-color: unset;">GMP</td> <td class="lt-bio-3791" style="background-color: unset;">GDP</td> <td class="lt-bio-3791" style="background-color: unset;">GTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;">Cytosine (C)</td> <td class="lt-bio-3791" style="background-color: unset;">Cytidine</td> <td class="lt-bio-3791" style="background-color: unset;">CMP</td> <td class="lt-bio-3791" style="background-color: unset;">CDP</td> <td class="lt-bio-3791" style="background-color: unset;">CTP</td> </tr> <tr> <td class="lt-bio-3791" style="background-color: unset;">Uracil (U)</td> <td class="lt-bio-3791" style="background-color: unset;">Uridine</td> <td class="lt-bio-3791" style="background-color: unset;">UMP</td> <td class="lt-bio-3791" style="background-color: unset;">UDP</td> <td class="lt-bio-3791" style="background-color: unset;">UTP</td> </tr> </tbody>
</table>

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