{"id":647,"date":"2017-04-16T02:54:36","date_gmt":"2017-04-16T02:54:36","guid":{"rendered":"https:\/\/pressbooks.hccfl.edu\/bio1\/chapter\/7-1-energy-in-living-systems\/"},"modified":"2025-08-29T18:14:57","modified_gmt":"2025-08-29T18:14:57","slug":"7-1-energy-in-living-systems","status":"publish","type":"chapter","link":"https:\/\/pressbooks.hccfl.edu\/bio1\/chapter\/7-1-energy-in-living-systems\/","title":{"raw":"Energy in Living Systems","rendered":"Energy in Living Systems"},"content":{"raw":"All living organisms require energy to perform their life processes. Energy, as you learned earlier in the <a href=\"\/chapter\/6-6-enzymes\/\" target=\"_blank\" rel=\"noopener noreferrer\">chapter about enzymes<\/a>, is the ability to do work or to create some kind of change. You are familiar with or have learned about many processes that can require energy:\n<ul>\n \t<li>Movement<\/li>\n \t<li>Reproduction<\/li>\n \t<li>Maintaining homeostasis of many different conditions<\/li>\n \t<li>Acquiring and digesting food<\/li>\n \t<li>Producing proteins<\/li>\n<\/ul>\nJust as living things must continually consume food to replenish their energy supplies, cells must continually produce more energy to replenish that used by the many energy-requiring chemical reactions that constantly take place. Together, all of the chemical reactions that take place inside cells, including those that consume or generate energy, are referred to as the cell\u2019s\u00a0<strong>metabolism<\/strong>.\n\nA living cell cannot store significant amounts of free energy. Free energy is energy that is not stored in molecules. Excess free energy would result in an increase of heat in the cell, which would denature enzymes and other proteins, and destroy the cell. Instead, a cell must be able to store energy safely and release it for use only as needed. Living cells accomplish this using ATP, which can be used to fill any energy need of the cell. How? It functions like a rechargeable battery.\n\nWhen ATP is broken down, energy is released. This energy is used by the cell to do work. For example, in the mechanical work of muscle contraction, ATP supplies energy to move the contractile muscle proteins.\n<h1>ATP Structure and Function<\/h1>\nATP is a complex-looking molecule, but for our purposes you can think of it as a rechargeable battery. ATP, the fully charged form of our battery,\u00a0is made up of\u00a0three phosphates (the \"TP\" part of ATP means \"tri phosphate\") attached to a sugar and an adenine (the \"A\" part of ATP) (<strong>Figure 1<\/strong>). When the last phosphate is broken off of the ATP, energy is released. The result is a single phosphate and a molecule called ADP (\"D\" stands for \"di\" which means two).\n\n[caption id=\"attachment_110\" align=\"alignnone\" width=\"300\"]<img class=\"wp-image-110 size-medium\" src=\"http:\/\/pressbooks.hccfl.edu\/bio1\/wp-content\/uploads\/sites\/106\/2017\/04\/Figure_04_12-1-300x177-1.jpg\" alt=\"structure of ATP\" width=\"300\" height=\"177\"> <strong>Figure 1<\/strong> The structure of ATP shows the basic components of a two-ring adenine, five-carbon ribose sugar, and three phosphate groups.[\/caption]\n\nA large amount of energy is required in order to recharge a molecule of ADP into ATP. This energy is stored in the bond between the second and third phosphates. When this bond is broken, the energy is released in a way that the cell can use it.\n\n[h5p id=\"144\"]\n<h1>References<\/h1>\nUnless otherwise noted, images on this page are licensed under <a href=\"https:\/\/mobile.mhcc.edu\/owa\/redir.aspx?C=fELq4h6Pt0ZToj0GTMFwdPEQ6w28kY5ckgbKyG9QmZ496IJSvdzTCA..&amp;URL=https%3a%2f%2fcreativecommons.org%2flicenses%2fby%2f4.0%2f\" target=\"_blank\" rel=\"noopener noreferrer\">CC-BY 4.0<\/a>\u00a0by\u00a0<a href=\"https:\/\/mobile.mhcc.edu\/owa\/redir.aspx?C=A5cEwLWl1r7AYbXIMefCCq5lXEDIZngk0oVPYclrOlQ96IJSvdzTCA..&amp;URL=https%3a%2f%2fopenstax.org%2f\" target=\"_blank\" rel=\"noopener noreferrer\">OpenStax<\/a>.\n\n<span class=\"name\">Text adapted from: OpenStax<\/span>, Concepts of Biology. OpenStax CNX. May 18, 2016 http:\/\/cnx.org\/contents\/b3c1e1d2-839c-42b0-a314-e119a8aafbdd@9.10","rendered":"<p>All living organisms require energy to perform their life processes. Energy, as you learned earlier in the <a href=\"\/chapter\/6-6-enzymes\/\" target=\"_blank\" rel=\"noopener noreferrer\">chapter about enzymes<\/a>, is the ability to do work or to create some kind of change. You are familiar with or have learned about many processes that can require energy:<\/p>\n<ul>\n<li>Movement<\/li>\n<li>Reproduction<\/li>\n<li>Maintaining homeostasis of many different conditions<\/li>\n<li>Acquiring and digesting food<\/li>\n<li>Producing proteins<\/li>\n<\/ul>\n<p>Just as living things must continually consume food to replenish their energy supplies, cells must continually produce more energy to replenish that used by the many energy-requiring chemical reactions that constantly take place. Together, all of the chemical reactions that take place inside cells, including those that consume or generate energy, are referred to as the cell\u2019s\u00a0<strong>metabolism<\/strong>.<\/p>\n<p>A living cell cannot store significant amounts of free energy. Free energy is energy that is not stored in molecules. Excess free energy would result in an increase of heat in the cell, which would denature enzymes and other proteins, and destroy the cell. Instead, a cell must be able to store energy safely and release it for use only as needed. Living cells accomplish this using ATP, which can be used to fill any energy need of the cell. How? It functions like a rechargeable battery.<\/p>\n<p>When ATP is broken down, energy is released. This energy is used by the cell to do work. For example, in the mechanical work of muscle contraction, ATP supplies energy to move the contractile muscle proteins.<\/p>\n<h1>ATP Structure and Function<\/h1>\n<p>ATP is a complex-looking molecule, but for our purposes you can think of it as a rechargeable battery. ATP, the fully charged form of our battery,\u00a0is made up of\u00a0three phosphates (the &#8220;TP&#8221; part of ATP means &#8220;tri phosphate&#8221;) attached to a sugar and an adenine (the &#8220;A&#8221; part of ATP) (<strong>Figure 1<\/strong>). When the last phosphate is broken off of the ATP, energy is released. The result is a single phosphate and a molecule called ADP (&#8220;D&#8221; stands for &#8220;di&#8221; which means two).<\/p>\n<figure id=\"attachment_110\" aria-describedby=\"caption-attachment-110\" style=\"width: 300px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-110 size-medium\" src=\"http:\/\/pressbooks.hccfl.edu\/bio1\/wp-content\/uploads\/sites\/106\/2017\/04\/Figure_04_12-1-300x177-1.jpg\" alt=\"structure of ATP\" width=\"300\" height=\"177\" \/><figcaption id=\"caption-attachment-110\" class=\"wp-caption-text\"><strong>Figure 1<\/strong> The structure of ATP shows the basic components of a two-ring adenine, five-carbon ribose sugar, and three phosphate groups.<\/figcaption><\/figure>\n<p>A large amount of energy is required in order to recharge a molecule of ADP into ATP. This energy is stored in the bond between the second and third phosphates. When this bond is broken, the energy is released in a way that the cell can use it.<\/p>\n<div id=\"h5p-144\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-144\" class=\"h5p-iframe\" data-content-id=\"144\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"ATP\"><\/iframe><\/div>\n<\/div>\n<h1>References<\/h1>\n<p>Unless otherwise noted, images on this page are licensed under <a href=\"https:\/\/mobile.mhcc.edu\/owa\/redir.aspx?C=fELq4h6Pt0ZToj0GTMFwdPEQ6w28kY5ckgbKyG9QmZ496IJSvdzTCA..&amp;URL=https%3a%2f%2fcreativecommons.org%2flicenses%2fby%2f4.0%2f\" target=\"_blank\" rel=\"noopener noreferrer\">CC-BY 4.0<\/a>\u00a0by\u00a0<a href=\"https:\/\/mobile.mhcc.edu\/owa\/redir.aspx?C=A5cEwLWl1r7AYbXIMefCCq5lXEDIZngk0oVPYclrOlQ96IJSvdzTCA..&amp;URL=https%3a%2f%2fopenstax.org%2f\" target=\"_blank\" rel=\"noopener noreferrer\">OpenStax<\/a>.<\/p>\n<p><span class=\"name\">Text adapted from: OpenStax<\/span>, Concepts of Biology. OpenStax CNX. May 18, 2016 http:\/\/cnx.org\/contents\/b3c1e1d2-839c-42b0-a314-e119a8aafbdd@9.10<\/p>\n","protected":false},"author":130,"menu_order":1,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["lisa-bartee-8iamvryfkq","shriner-waiter-s570sonk1t","catherine-creech-qsectufgaw"],"pb_section_license":"cc-by"},"chapter-type":[],"contributor":[85,83,84],"license":[53],"class_list":["post-647","chapter","type-chapter","status-publish","hentry","contributor-catherine-creech-qsectufgaw","contributor-lisa-bartee-8iamvryfkq","contributor-shriner-waiter-s570sonk1t","license-cc-by"],"part":644,"_links":{"self":[{"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/647","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/wp\/v2\/users\/130"}],"version-history":[{"count":2,"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/647\/revisions"}],"predecessor-version":[{"id":718,"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/647\/revisions\/718"}],"part":[{"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/pressbooks\/v2\/parts\/644"}],"metadata":[{"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/647\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/wp\/v2\/media?parent=647"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapter-type?post=647"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/wp\/v2\/contributor?post=647"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.hccfl.edu\/bio1\/wp-json\/wp\/v2\/license?post=647"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}