{"id":115,"date":"2017-08-16T09:04:15","date_gmt":"2017-08-16T09:04:15","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/biology\/?page_id=115"},"modified":"2017-08-17T09:32:31","modified_gmt":"2017-08-17T09:32:31","slug":"lipids","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/biology\/lipids\/","title":{"rendered":"Lipids"},"content":{"rendered":"<div class=\"twelve columns\" style=\"margin-top: 10%;\">\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/biochemical-basis-of-life-2\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/biochemical-basis-of-life\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/proteins\">Next Lesson \u27a1<\/a><\/div>\n<p><!-- CONTENT BEGINS HERE --><\/p>\n<h1 id=\"title\">Lipids<\/h1>\n<h4>Objective<\/h4>\n<p>In this lesson, you will review lipids.<\/p>\n<h4>Previously covered:<\/h4>\n<ul>\n<li>Living things store energy in the carbon bonds of organic molecules.<\/li>\n<li>Organic compounds that contain many methyl groups tend to be insoluble in water.<\/li>\n<li>Organic compounds containing a carboxyl group act as acids.<\/li>\n<li>An organic compound called an ester is formed by a condensation reaction between an alcohol and an acid.<\/li>\n<\/ul>\n<section>\n<h3>Fats and Oils and Waxes \u2013 Oh, my!<\/h3>\n<p>Lipids all contain long chains or rings of hydrocarbons that give them their relatively <abbr title=\"lacking a strong attraction to water, examples include waxes, oils, and fats\">hydrophobic<\/abbr> and <abbr title=\"substance that has an equal distribution of electrons between atoms or symmetrical shape so that no part of the molecule is more positive or negative\">non-polar<\/abbr> characteristics. Examples of lipids include fats and oils, waxes, phospholipids, and ringed steroids, such as cholesterol and steroid hormones. Lipids are important components of cell membranes. They serve as a form of long-term energy storage, act in transport, and function as chemical messengers.<\/p>\n<p>Fats and oils are triglycerides, esters of glycerol, and fatty acids. They are formed in dehydration synthesis reactions. Triglycerides are the primary form of long-term energy storage in plants and animals. Fatty acids are long chains of 12 to 24 hydrocarbons with a carboxyl group at the end. Bonding within fatty acid chains gives fats and oils their characteristics.<\/p>\n<p><img decoding=\"async\" class=\"u-pull-left padding\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/saturatedunsaturaded.jpg\" alt=\"Saturated and unsaturated fats\" \/><\/p>\n<p>Fats and oils can be classified as <abbr title=\"a solution that has all the solute dissolved that can be physically dissolved in that solution; for electrons, saturation occurs when one electron is shared per atom as apposed to two electrons shared with two atoms (a double bond) therefore there are only single bonds present in the hydrocarbons\">saturated<\/abbr>, <abbr title=\"a fatty acid or oil which contains a double or triple bond for each molecule\">monounsaturated<\/abbr>, or <abbr title=\"comprised of multiple double or triple bonds within a molecule of a fatty acid or oil as compared to monounsaturated\">polyunsaturated<\/abbr>, depending on the number of double bonds between carbon atoms in the fatty acid chains.<\/p>\n<p>Animal fats have all single-carbon bonds and so are bonded to the maximum number of hydrogen atoms possible. The single bonds form a straight fatty acid chain. They are called <em>saturated<\/em> fats and are solid at room temperature.<\/p>\n<p>Oils have some double bonding of carbon atoms and so are <em>unsaturated<\/em> fats. The double bonds create bends in the fatty acid tails, which makes unsaturated fats liquid at room temperature.<\/p>\n<p><em>Polyunsaturated<\/em> fats have multiple double bonded carbons.<\/p>\n<p><img decoding=\"async\" class=\"u-pull-left padding\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/phospholipid.jpg\" alt=\"Hydrophobic and hydrophilic parts of a phospholipid\" \/><\/p>\n<p>Waxes are also esters of long chain fatty acids bonded to long chain alcohols. Waxes function to provide a waterproof coating on many living things. Plant cuticles are waxy, as are many of the oils secreted by the skin. The exoskeleton of insects contains wax.<\/p>\n<p>Phospholipids are composed of glycerol, two fatty acids, and a phosphate head. The fatty acid tails of the molecule are hydrophobic, while the phosphate end of the molecule is <abbr title=\"molecular structure having one or more poles that attract opposites to each other, as in phospholids, where the polar heads arrange themselves opposite each other to create an oily membrane interior\">polar<\/abbr> and <abbr title=\"having a strong attraction to water\">hydrophilic<\/abbr>. This arrangement is ideal for function in double-layered cell membranes. In solution and in cells, the polar heads of phospholipids arrange themselves opposite each other, creating an oily membrane interior. The unique structure of phospholipid bilayers makes them selectively permeable.<\/p>\n<p><abbr title=\"\">Steroids<\/abbr> all contain a core consisting of four fused hydrocarbon rings. Examples of steroids include cholesterol, steroid hormones, and vitamins. Steroids are differentiated by the unique groups bonded at the outer regions of the four ring core.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/biology\/wp-content\/uploads\/sites\/2\/2017\/08\/BioMod31.3_cholesterol.jpg\" alt=\"Steroid core and cholesterols\" \/><\/center><em>Cholesterol<\/em> is an important component of cell membranes. It gives membranes their fluidity. In humans, the liver processes cholesterol in order to produce bile. Precipitated cholesterol can produce gall stones. Excess cholesterol in the blood can lead to cardiovascular disease.<\/p>\n<p><em>Hormones<\/em> are chemical signals that act only on cells with specific receptors. Steroid hormones include the sex hormones estrogen, progesterone, and testosterone. Cortisone is also a steroid hormone, which is important in carbohydrate metabolism. It has anti-inflammatory properties that make it important in treatment of some diseases. A group of similar steroids acts as vitamin D.<\/p>\n<p><em>Lipoproteins<\/em> are composed of proteins and several types of lipids bonded together. Some lipoproteins serve as catalysts, and many are associated with membrane-bound proteins. Some lipoproteins function to transport other lipids, such as cholesterol and steroids, throughout the body. Lipoproteins are classified based on their density. High-density lipoprotein (HDL) transports cholesterol to the liver. Low-density lipoprotein (LDL) transports cholesterol to body tissues. Very low-density lipoprotein (VLDL) transports triglycerides for storage as fat.<\/p>\n<h3>Summary<\/h3>\n<ul>\n<li>Lipids are non-polar and insoluble in water.<\/li>\n<li>Phospholipids and the steroid cholesterol are important components of cell membranes.<\/li>\n<li>Triglycerides are esters that provide a form of long-term energy storage.<\/li>\n<li>Lipoproteins act in transport, and some steroids function as vitamins or chemical messengers.<\/li>\n<\/ul>\n<\/section>\n<p><!-- CONTENT ENDS HERE --><\/p>\n<div class=\"advance\"><a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/biochemical-basis-of-life-2\">\u2b05 Previous Lesson<\/a>\u00a0<a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/biochemical-basis-of-life\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/biology\/proteins\">Next Lesson \u27a1<\/a><\/div>\n<p><a class=\"backtotop\" href=\"#title\">Back to Top<\/a><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u2b05 Previous Lesson\u00a0Workshop Index\u00a0Next Lesson \u27a1 Lipids Objective In this lesson, you will review lipids. Previously covered: Living things store energy in the carbon bonds of organic molecules. Organic compounds that contain many methyl groups tend to be insoluble in water. Organic compounds containing a carboxyl group act as acids. An organic compound called an [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-115","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages\/115","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/comments?post=115"}],"version-history":[{"count":5,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages\/115\/revisions"}],"predecessor-version":[{"id":600,"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/pages\/115\/revisions\/600"}],"wp:attachment":[{"href":"https:\/\/americanboard.org\/Subjects\/biology\/wp-json\/wp\/v2\/media?parent=115"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}