{"id":2653,"date":"2016-06-06T20:54:53","date_gmt":"2016-06-06T20:54:53","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/biologyxwaymakerxmaster\/?post_type=chapter&#038;p=2653"},"modified":"2024-04-26T00:28:22","modified_gmt":"2024-04-26T00:28:22","slug":"reading-ribosomes","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/chapter\/reading-ribosomes\/","title":{"raw":"Requirements for Translation","rendered":"Requirements for Translation"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Describe the components needed for translation<\/li>\r\n<\/ul>\r\n<\/div>\r\n\r\n[caption id=\"attachment_1459\" align=\"alignright\" width=\"342\"]<img class=\"wp-image-1459\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02190956\/Figure_15_05_01.jpg\" alt=\"Illustration shows two amino acids side-by-side. Each amino acid has an amino group, a carboxyl group, and a side chain labeled R or R'. Upon formation of a peptide bond, the amino group is joined to the carboxyl group. A water molecule is released in the process.\" width=\"342\" height=\"246\" \/> Figure 1. A peptide bond links the carboxyl end of one amino acid with the amino end of another, expelling one water molecule. For simplicity in this image, only the functional groups involved in the peptide bond are shown. The R and R\u2032 designations refer to the rest of each amino acid structure.[\/caption]\r\n\r\nThe process of translation, or protein synthesis, involves the decoding of an mRNA message into a polypeptide product. Amino acids are covalently strung together by interlinking <span style=\"text-decoration: underline;\">peptide bonds<\/span>.\u00a0Each individual amino acid has an amino group (NH<sub>2<\/sub>) and a carboxyl (COOH) group. Polypeptides are formed when the amino group of one amino acid forms an amide (i.e., peptide) bond with the carboxyl group of another amino acid (Figure 1).\r\n\r\nThis reaction is catalyzed by ribosomes and generates one water molecule.\r\n<h2>The Protein Synthesis Machinery<\/h2>\r\nIn addition to the mRNA template, many molecules and macromolecules contribute to the process of translation.\u00a0 Translation requires the input of an <strong>mRNA template<\/strong>, <strong>ribosomes<\/strong>, <strong>tRNAs<\/strong>, and various enzymatic factors.\r\n<div class=\"textbox shaded\"><a href=\"https:\/\/www.pbs.org\/wgbh\/aso\/tryit\/dna\/protein.html\" target=\"_blank\" rel=\"noopener\">Click through the steps of this\u00a0PBS interactive to see protein synthesis in action.<\/a><\/div>\r\n<h3>Ribosomes<\/h3>\r\nA ribosome is a complex macromolecule composed of structural and catalytic rRNAs, and many distinct polypeptides. Ribosomes exist in the cytoplasm in prokaryotes and in the cytoplasm and rough endoplasmic reticulum in eukaryotes.\u00a0\u00a0 Ribosomes are made up of two subunits.\u00a0 In\u00a0<em>E. coli<\/em>, the small subunit is described as 30S, and the large subunit is 50S, for a total of 70S. Mammalian ribosomes have a small 40S subunit and a large 60S subunit, for a total of 80S. The small subunit is responsible for binding the mRNA template, whereas the large subunit sequentially binds tRNAs.\r\n<h3>tRNAs<\/h3>\r\nThe tRNAs are structural RNA molecules that were transcribed from genes by RNA polymerase III.\u00a0 Serving as adaptors, specific tRNAs bind to sequences on the mRNA template and add the corresponding amino acid to the polypeptide chain. Therefore, tRNAs are the molecules that actually \"translate\" the language of RNA into the language of proteins.\r\n\r\n[caption id=\"attachment_1457\" align=\"alignright\" width=\"400\"]<img class=\"wp-image-1457\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02190850\/Figure_15_04_03.jpg\" alt=\"The molecular model of phenylalanine tRNA is L-shaped. At one end is the anticodon AAG. At the other end is the attachment site for the amino acid phenylalanine\" width=\"400\" height=\"528\" \/> Figure 2. Phenylalanine tRNA[\/caption]\r\n\r\nOf the 64 possible mRNA codons\u2014or triplet combinations of A, U, G, and C\u2014three specify the termination of protein synthesis and 61 specify the addition of amino acids to the polypeptide chain. Of these 61, one codon (AUG) also known as the \"start codon\" encodes the initiation of translation. Each tRNA anticodon can base pair with one of the mRNA codons and add an amino acid or terminate translation, according to the genetic code. For instance, if the sequence CUA occurred on an mRNA template in the proper reading frame, it would bind a tRNA expressing the complementary sequence, GAU, which would be linked to the amino acid leucine.\r\n\r\nMature tRNAs take on a three-dimensional structure through intramolecular hydrogen bonding to position the amino acid binding site at one end and the\u00a0<strong>anticodon<\/strong> at the other end (Figure 2).The anticodon is a three-nucleotide sequence in a tRNA that interacts with an mRNA codon through complementary base pairing.\r\n\r\ntRNAs need to interact with three factors:\r\n<ol>\r\n \t<li>They must be recognized by the correct aminoacyl synthetase.<\/li>\r\n \t<li>They must be recognized by ribosomes.<\/li>\r\n \t<li>They must bind to the correct sequence in mRNA.<\/li>\r\n<\/ol>\r\n<h3>Aminoacyl tRNA Synthetases<\/h3>\r\nThrough the process of tRNA \"charging,\" each tRNA molecule is linked to its correct amino acid by a group of enzymes called <span style=\"text-decoration: underline;\">aminoacyl tRNA synthetases<\/span>. At least one type of\u00a0<strong>aminoacyl tRNA synthetase<\/strong> exists for each of the 20 amino acids.\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/d58239a2-332f-4d75-bca7-2b5db1ae18aa\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Describe the components needed for translation<\/li>\n<\/ul>\n<\/div>\n<div id=\"attachment_1459\" style=\"width: 352px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1459\" class=\"wp-image-1459\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02190956\/Figure_15_05_01.jpg\" alt=\"Illustration shows two amino acids side-by-side. Each amino acid has an amino group, a carboxyl group, and a side chain labeled R or R'. Upon formation of a peptide bond, the amino group is joined to the carboxyl group. A water molecule is released in the process.\" width=\"342\" height=\"246\" \/><\/p>\n<p id=\"caption-attachment-1459\" class=\"wp-caption-text\">Figure 1. A peptide bond links the carboxyl end of one amino acid with the amino end of another, expelling one water molecule. For simplicity in this image, only the functional groups involved in the peptide bond are shown. The R and R\u2032 designations refer to the rest of each amino acid structure.<\/p>\n<\/div>\n<p>The process of translation, or protein synthesis, involves the decoding of an mRNA message into a polypeptide product. Amino acids are covalently strung together by interlinking <span style=\"text-decoration: underline;\">peptide bonds<\/span>.\u00a0Each individual amino acid has an amino group (NH<sub>2<\/sub>) and a carboxyl (COOH) group. Polypeptides are formed when the amino group of one amino acid forms an amide (i.e., peptide) bond with the carboxyl group of another amino acid (Figure 1).<\/p>\n<p>This reaction is catalyzed by ribosomes and generates one water molecule.<\/p>\n<h2>The Protein Synthesis Machinery<\/h2>\n<p>In addition to the mRNA template, many molecules and macromolecules contribute to the process of translation.\u00a0 Translation requires the input of an <strong>mRNA template<\/strong>, <strong>ribosomes<\/strong>, <strong>tRNAs<\/strong>, and various enzymatic factors.<\/p>\n<div class=\"textbox shaded\"><a href=\"https:\/\/www.pbs.org\/wgbh\/aso\/tryit\/dna\/protein.html\" target=\"_blank\" rel=\"noopener\">Click through the steps of this\u00a0PBS interactive to see protein synthesis in action.<\/a><\/div>\n<h3>Ribosomes<\/h3>\n<p>A ribosome is a complex macromolecule composed of structural and catalytic rRNAs, and many distinct polypeptides. Ribosomes exist in the cytoplasm in prokaryotes and in the cytoplasm and rough endoplasmic reticulum in eukaryotes.\u00a0\u00a0 Ribosomes are made up of two subunits.\u00a0 In\u00a0<em>E. coli<\/em>, the small subunit is described as 30S, and the large subunit is 50S, for a total of 70S. Mammalian ribosomes have a small 40S subunit and a large 60S subunit, for a total of 80S. The small subunit is responsible for binding the mRNA template, whereas the large subunit sequentially binds tRNAs.<\/p>\n<h3>tRNAs<\/h3>\n<p>The tRNAs are structural RNA molecules that were transcribed from genes by RNA polymerase III.\u00a0 Serving as adaptors, specific tRNAs bind to sequences on the mRNA template and add the corresponding amino acid to the polypeptide chain. Therefore, tRNAs are the molecules that actually &#8220;translate&#8221; the language of RNA into the language of proteins.<\/p>\n<div id=\"attachment_1457\" style=\"width: 410px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1457\" class=\"wp-image-1457\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02190850\/Figure_15_04_03.jpg\" alt=\"The molecular model of phenylalanine tRNA is L-shaped. At one end is the anticodon AAG. At the other end is the attachment site for the amino acid phenylalanine\" width=\"400\" height=\"528\" \/><\/p>\n<p id=\"caption-attachment-1457\" class=\"wp-caption-text\">Figure 2. Phenylalanine tRNA<\/p>\n<\/div>\n<p>Of the 64 possible mRNA codons\u2014or triplet combinations of A, U, G, and C\u2014three specify the termination of protein synthesis and 61 specify the addition of amino acids to the polypeptide chain. Of these 61, one codon (AUG) also known as the &#8220;start codon&#8221; encodes the initiation of translation. Each tRNA anticodon can base pair with one of the mRNA codons and add an amino acid or terminate translation, according to the genetic code. For instance, if the sequence CUA occurred on an mRNA template in the proper reading frame, it would bind a tRNA expressing the complementary sequence, GAU, which would be linked to the amino acid leucine.<\/p>\n<p>Mature tRNAs take on a three-dimensional structure through intramolecular hydrogen bonding to position the amino acid binding site at one end and the\u00a0<strong>anticodon<\/strong> at the other end (Figure 2).The anticodon is a three-nucleotide sequence in a tRNA that interacts with an mRNA codon through complementary base pairing.<\/p>\n<p>tRNAs need to interact with three factors:<\/p>\n<ol>\n<li>They must be recognized by the correct aminoacyl synthetase.<\/li>\n<li>They must be recognized by ribosomes.<\/li>\n<li>They must bind to the correct sequence in mRNA.<\/li>\n<\/ol>\n<h3>Aminoacyl tRNA Synthetases<\/h3>\n<p>Through the process of tRNA &#8220;charging,&#8221; each tRNA molecule is linked to its correct amino acid by a group of enzymes called <span style=\"text-decoration: underline;\">aminoacyl tRNA synthetases<\/span>. At least one type of\u00a0<strong>aminoacyl tRNA synthetase<\/strong> exists for each of the 20 amino acids.<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_d58239a2-332f-4d75-bca7-2b5db1ae18aa\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/d58239a2-332f-4d75-bca7-2b5db1ae18aa?iframe_resize_id=assessment_practice_id_d58239a2-332f-4d75-bca7-2b5db1ae18aa\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-2653\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology. <strong>Provided by<\/strong>: OpenStax CNX. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":6,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology\",\"author\":\"\",\"organization\":\"OpenStax CNX\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\"}]","CANDELA_OUTCOMES_GUID":"4b4adefc-1b80-4871-8d3c-3ffb55f34504, 7792ad8c-5829-44c8-8bf7-a1b89935c920","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-2653","chapter","type-chapter","status-publish","hentry"],"part":316,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/pressbooks\/v2\/chapters\/2653","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":15,"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/pressbooks\/v2\/chapters\/2653\/revisions"}],"predecessor-version":[{"id":6776,"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/pressbooks\/v2\/chapters\/2653\/revisions\/6776"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/pressbooks\/v2\/parts\/316"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/pressbooks\/v2\/chapters\/2653\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/wp\/v2\/media?parent=2653"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/pressbooks\/v2\/chapter-type?post=2653"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/wp\/v2\/contributor?post=2653"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/wp-json\/wp\/v2\/license?post=2653"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}