{"id":4368,"date":"2019-06-17T18:07:27","date_gmt":"2019-06-17T18:07:27","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/3-7-nucleic-acids-3\/"},"modified":"2023-11-30T17:50:33","modified_gmt":"2023-11-30T17:50:33","slug":"3-7-nucleic-acids-3","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/acchumanbio\/chapter\/3-7-nucleic-acids-3\/","title":{"raw":"3.7 Nucleic Acids","rendered":"3.7 Nucleic Acids"},"content":{"raw":" \r\n

Who's Who?<\/h1>\r\n[h5p id=\"459\"]\r\n\r\nFigure 3.7.1 Identical twins show clearly the importance of genes in making us who we are. Genes would not be possible without nucleic acids.<\/em>\r\n
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What Are Nucleic Acids?<\/h1>\r\n<\/div>\r\n[pb_glossary id=\"5475\"]Nucleic acids[\/pb_glossary]<\/strong>\u00a0are the class of\u00a0biochemical compounds\u00a0that includes\u00a0DNA and RNA. These molecules are built of small monomers called\u00a0[pb_glossary id=\"518\"]nucleotides[\/pb_glossary]<\/strong>. Many nucleotides bind together to form a chain called a\u00a0polynucleotide. The\u00a0nucleic acid\u00a0[pb_glossary id=\"277\"]DNA[\/pb_glossary]<\/strong>\u00a0(deoxyribonucleic acid) consists of two polynucleotide chains or strands. Thus,\u00a0DNA\u00a0is sometimes called double-stranded. The\u00a0nucleic acid\u00a0[pb_glossary id=\"519\"]RNA[\/pb_glossary]<\/strong>\u00a0(ribonucleic acid) consists of just one polynucleotide chain or strand, so\u00a0RNA\u00a0is sometimes called single-stranded.\r\n
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Structure of Nucleic Acids<\/h1>\r\n<\/div>\r\nEach nucleotide consists of three smaller molecules:\r\n
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  1. A sugar molecule (the sugar d<\/span>eoxyribose in\u00a0D<\/span>NA\u00a0and the sugar r<\/span>ibose in R<\/span>NA)<\/li>\r\n \t
  2. A phosphate group<\/li>\r\n \t
  3. A nitrogen base<\/li>\r\n<\/ol>\r\nThe nitrogen bases in a\u00a0nucleic acid\u00a0stick out from the backbone. There are four different nitrogen bases: cytosine, adenine, guanine, and either thymine (in DNA) or uracil (in RNA). In DNA, bonds form between bases on the two nucleotide chains and hold the chains together. Each type of\u00a0base binds with just one other type of base: cytosine always binds with guanine, and adenine always binds with thymine. These pairs of bases are called\u00a0[pb_glossary id=\"528\"]complementary<\/strong>\u00a0<\/strong>base\u00a0<\/strong>\u00a0<\/strong>pairs<\/strong>[\/pb_glossary].\r\n\r\n[caption id=\"attachment_525\" align=\"aligncenter\" width=\"485\"]\"A Figure 3.7.2 A short section of DNA showing complementary base pairing.<\/em>[\/caption]\r\n\r\n
    \r\n\r\nAs you can see in Figure 3.7.2, sugars and phosphate groups form the backbone of a polynucleotide chain. Hydrogen bonds between complementary bases hold the two polynucleotide chains together.\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_329\" align=\"alignright\" width=\"290\"]\"A Figure 3.7.3 DNA is a polymer made of many monomers called nucleotides. DNA carries all the instructions a cell needs to carry out metabolism.<\/em>[\/caption]\r\n\r\nThe binding of complementary bases causes DNA molecules automatically to take their well-known\u00a0[pb_glossary id=\"5525\"]double helix[\/pb_glossary]<\/strong> shape, which is shown in the animation in Figure 3.7.3. A double helix is like a spiral staircase. It forms naturally and is very strong, making the two polynucleotide chains difficult to break apart.\r\n\r\nDNA Molecule. Hydrogen bonds between complementary bases help form the double helix of a DNA molecule. The letters A, T, G, and C stand for the bases adenine, thymine, guanine, and cytosine. The sequence of these four bases in DNA is a code that carries instructions for making proteins. Shown is a representation of how the double helix folds into a chromosome.<\/span>\r\n\r\n \r\n
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    Roles of Nucleic Acids<\/h1>\r\n<\/div>\r\n[pb_glossary id=\"277\"]DNA[\/pb_glossary] makes up genes, and the sequence of bases in DNA makes up the\u00a0genetic code. Between \u201cstarts\u201d and \u201cstops,\u201d the code carries instructions for the correct sequence of\u00a0[pb_glossary id=\"5707\"]amino acids[\/pb_glossary]\u00a0in a\u00a0protein.\u00a0[pb_glossary id=\"519\"]RNA[\/pb_glossary]\u00a0uses the information in DNA to assemble the correct amino acids and help make the [pb_glossary id=\"5813\"]protein[\/pb_glossary]. The information in DNA is passed from parent\u00a0cells\u00a0to daughter cells whenever cells divide, and it is also passed from parents to offspring when organisms [pb_glossary id=\"5807\"]reproduce[\/pb_glossary]. This is how inherited characteristics are passed from one generation to the next.\r\n\r\n[caption id=\"attachment_1720\" align=\"alignright\" width=\"436\"]\"Image Figure 3.7.4 ATP (adenosine TRI phosphate) can be converted to ADP (adenosine DI phosphate) to release the energy stored in the chemical bonds between the second and third phosphate group.<\/em>[\/caption]\r\n

    ATP is Energy<\/h1>\r\nThere is one type of specialized nucleic acid that exists only as a [pb_glossary id=\"5781\"]monomer[\/pb_glossary].\u00a0 It stands apart from the other nucleic acids because it does not code for, or help create, proteins.\u00a0 \u00a0This molecule is [pb_glossary id=\"5549\"]ATP[\/pb_glossary]<\/strong>, which stands for adenosine triphosphate.\u00a0 It consists of a sugar, adenosine, and three phosphate groups.\u00a0 It's primary role is as the basic [pb_glossary id=\"5753\"]energy[\/pb_glossary] currency in the [pb_glossary id=\"5665\"]cell[\/pb_glossary].\u00a0 The way ATP works is all based on the phosphates.\u00a0 As shown in Figure 3.7.4, a large amount of energy is stored in the bond between the second and third phosphate group.\u00a0 When this bond is broken, it functions as an exothermic reaction and this energy can be used to power other processes taking place in the cell.\r\n
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    3.7 Summary<\/span><\/h1>\r\n<\/header>\r\n
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