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0px"><i class="fa fa-fw"></i><a href="membrane-structure-13-.html">Membrane structure 1.3 </a></label></li><li class=""><label style="padding-left: 0px"><i class="fa fa-fw"></i><a href="../575/membrane-transport-14-.html">Membrane transport 1.4 </a></label></li><li class=""><label style="padding-left: 0px"><i class="fa fa-fw"></i><a href="../608/the-origin-of-cells-15.html">The origin of cells 1.5</a></label></li><li class=""><label style="padding-left: 0px"><i class="fa fa-fw"></i><a href="../609/cell-division-16.html">Cell division 1.6</a></label></li></ul></div> <div class="hidden-xs hidden-sm"> <button class="btn btn-default btn-block text-xs-center" data-toggle="modal" data-target="#modal-feedback" style="margin-bottom: 10px"><i class="fa fa-send"></i> Feedback</button> </div> </div> <div class="col-md-9" id="main-column"> <h1 class="page_title"> Membrane structure 1.3 <a href="#" class="mark-page-favorite pull-right" data-pid="607" title="Mark as favorite" onclick="return false;"><i class="fa fa-star-o"></i></a> </h1> <ol class="breadcrumb"> <li><a href="../../../biology.html"><i class="fa fa-home"></i></a><i class="fa fa-fw fa-chevron-right divider"></i></li><li><a href="../462/01-cell-biology.html">01 Cell biology</a><i class="fa fa-fw fa-chevron-right divider"></i></li><li><span class="gray">Membrane structure 1.3 </span></li> <span class="pull-right" style="color: #555" title="Suggested study time: 30 minutes"><i class="fa fa-clock-o"></i> 30'</span> </ol> <article id="main-article"> <style type="text/css">ol.breadcrumb { margin-bottom: 0 }</style><div id="toc-1675505948" class="toc"><a href="#" class="toc-switcher" title="Show table of contents"><small><i class="fa fa-reorder"></i> Table of contents <span class="pull-right"><i class="fa fa-chevron-down"></i></span></small></a><ol><li><a href="#header-1" class="scroll-to" data-target="header-1">Summary list for topic 1.3 Membrane structure</a></li><li><a href="#header-2" class="scroll-to" data-target="header-2">Mindmaps</a></li><li><a href="#header-3" class="scroll-to" data-target="header-3">Skills video tutorial</a></li><li><a href="#header-4" class="scroll-to" data-target="header-4">Model answer</a></li><li><a href="#header-5" class="scroll-to" data-target="header-5">Model answer:</a></li><li><a href="#header-6" class="scroll-to" data-target="header-6">Multiple choice quiz</a><ol></ol></li><li><a href="#header-7" class="scroll-to" data-target="header-7"> 1.3 Membrane structure 1/1 </a></li></ol><li><a href="#header-8" class="scroll-to" data-target="header-8">Drag and drop activities</a></li></div><div class="intro-card" readonly="false"><img alt="" src="../../images/01_cells/membrane_transport_modelsmall-1.jpg" style="float: left; width: 133px; height: 100px;">The first models of membranes included protein and phospholipids but not in the same structure as we see them today. In this topic the components of cell membranes are investigated and the structure of the membranes as fluid and dynamic structures is outlined.</div> <div class="panel panel-turquoise"> <div class="panel-heading"><a class="expander pull-right" href="#"><span class="fa fa-plus"></span></a> <div> <p>Key concepts</p> </div> </div> <div class="panel-body"> <div> <p>Learn and test your biological vocabulary for Membrane structure 1.3 using these flash cards </p> <p><iframe frameborder="0" height="420" scrolling="no" src="https://quizlet.com/51855022/flashcards/embed" width="100%"><br> </iframe></p> </div> </div> <div class="panel-footer"> <div> <p>text</p> </div> </div> </div> <div class="panel panel-default"> <div class="panel-footer"> <div> <p>text</p> </div> </div> </div> <div class="panel panel-yellow"> <div class="panel-heading"><a class="expander pull-right" href="#"><span class="fa fa-plus"></span></a> <div> <p>Essentials</p> </div> </div> <div class="panel-body"> <div> <p>These slides summarise the essential understanding and skills in this topic. <br> They contain short explanations in text and images - good revision for all students.</p> <p>Read the slides and look up any words or details you find difficult to understand.</p> <div id="carousel-75" class="dynamic-gallery carousel slide" data-id="75"><div class="carousel-inner" role="listbox"><div class="item active"><a class="fancy" href="../../../std-galleries/5-75/img1.png" data-fancybox="gallery-75" title="" data-caption=""><img alt="" src="../../../std-galleries/5-75/img1.png"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-75/img2.png" data-fancybox="gallery-75" title="" data-caption=""><img alt="" src="../../../std-galleries/5-75/img2.png"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-75/img3.png" data-fancybox="gallery-75" title="" data-caption=""><img alt="" src="../../../std-galleries/5-75/img3.png"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-75/img4.png" data-fancybox="gallery-75" title="" data-caption=""><img alt="" src="../../../std-galleries/5-75/img4.png"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-75/img5.png" data-fancybox="gallery-75" title="" data-caption=""><img alt="" src="../../../std-galleries/5-75/img5.png"></a></div></div><a class="left carousel-control" href="#carousel-75" role="button" data-slide="prev"><i class="fa fa-fw fa-chevron-left"></i></a><a class="right carousel-control" href="#carousel-75" role="button" data-slide="next"><i class="fa fa-fw fa-chevron-right"></i></a></div><ol class="std-carousel-indicators"><li data-index="0"><img title="Click to view" src="../../../std-galleries/5-75/img1-thumb128.jpg"><li><li data-index="1"><img title="Click to view" src="../../../std-galleries/5-75/img2-thumb128.jpg"><li><li data-index="2"><img title="Click to view" src="../../../std-galleries/5-75/img3-thumb128.jpg"><li><li data-index="3"><img title="Click to view" src="../../../std-galleries/5-75/img4-thumb128.jpg"><li><li data-index="4"><img title="Click to view" src="../../../std-galleries/5-75/img5-thumb128.jpg"><li></li></ol> </div> </div> <div class="panel-footer"> <div> <p>These slides summarise the essential understanding and skills in this topic. <br> They contain short explanations in text and images - great revision.</p> <p>Read the slides and look up any words or details you find difficult to understand.</p> <div id="carousel-210" class="dynamic-gallery carousel slide" data-id="210"><div class="carousel-inner" role="listbox"><div class="item active"><a class="fancy" href="../../../std-galleries/5-210/112movement-1.jpg" data-fancybox="gallery-210" title="" data-caption=""><img alt="" src="../../../std-galleries/5-210/112movement-1.jpg"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-210/112movement-2.jpg" data-fancybox="gallery-210" title="" data-caption=""><img alt="" src="../../../std-galleries/5-210/112movement-2.jpg"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-210/112movement-3.jpg" data-fancybox="gallery-210" title="" data-caption=""><img alt="" src="../../../std-galleries/5-210/112movement-3.jpg"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-210/112movement-4.jpg" data-fancybox="gallery-210" title="" data-caption=""><img alt="" src="../../../std-galleries/5-210/112movement-4.jpg"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-210/112movement-5.jpg" data-fancybox="gallery-210" title="" data-caption=""><img alt="" src="../../../std-galleries/5-210/112movement-5.jpg"></a></div></div><a class="left carousel-control" href="#carousel-210" role="button" data-slide="prev"><i class="fa fa-fw fa-chevron-left"></i></a><a class="right carousel-control" href="#carousel-210" role="button" data-slide="next"><i class="fa fa-fw fa-chevron-right"></i></a></div><ol class="std-carousel-indicators"><li data-index="0"><img title="Click to view" src="../../../std-galleries/5-210/112movement-1-thumb128.jpg"><li><li data-index="1"><img title="Click to view" src="../../../std-galleries/5-210/112movement-2-thumb128.jpg"><li><li data-index="2"><img title="Click to view" src="../../../std-galleries/5-210/112movement-3-thumb128.jpg"><li><li data-index="3"><img title="Click to view" src="../../../std-galleries/5-210/112movement-4-thumb128.jpg"><li><li data-index="4"><img title="Click to view" src="../../../std-galleries/5-210/112movement-5-thumb128.jpg"><li></li></ol> </div> </div> </div> <div class="panel panel-yellow"> <div class="panel-heading"><a class="expander" href="#"><span class="fa fa-plus"></span></a> <div> <p>Stretch for 7</p> </div> </div> <div class="panel-body"> <div> <p>These slides cover difficult parts of this topic - important if you are aiming for a high grade.<br> If grade 5 is your target, then save time, move on, study this information later, once you have revised the other topics.</p> <div id="carousel-77" class="dynamic-gallery carousel slide" data-id="77"><div class="carousel-inner" role="listbox"><div class="item active"><a class="fancy" href="../../../std-galleries/5-77/img102.png" data-fancybox="gallery-77" title="" data-caption=""><img alt="" src="../../../std-galleries/5-77/img102.png"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-77/img92.png" data-fancybox="gallery-77" title="" data-caption=""><img alt="" src="../../../std-galleries/5-77/img92.png"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-77/img8.png" data-fancybox="gallery-77" title="" data-caption=""><img alt="" src="../../../std-galleries/5-77/img8.png"></a></div></div><a class="left carousel-control" href="#carousel-77" role="button" data-slide="prev"><i class="fa fa-fw fa-chevron-left"></i></a><a class="right carousel-control" href="#carousel-77" role="button" data-slide="next"><i class="fa fa-fw fa-chevron-right"></i></a></div><ol class="std-carousel-indicators"><li data-index="0"><img title="Click to view" src="../../../std-galleries/5-77/img102-thumb128.jpg"><li><li data-index="1"><img title="Click to view" src="../../../std-galleries/5-77/img92-thumb128.jpg"><li><li data-index="2"><img title="Click to view" src="../../../std-galleries/5-77/img8-thumb128.jpg"><li></li></ol> </div> </div> <div class="panel-footer"> <div> </div> </div> </div> <div class="panel panel-violet"> <div class="panel-heading"><a class="expander pull-right" href="#"><span class="fa fa-plus"></span></a> <div> <p>Summary</p> </div> </div> <div class="panel-body"> <div> <h3 id="header-1">Summary list for topic 1.3 Membrane structure<small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h3> <ul> <li class="liWithoutP">Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules.</li> <li>Membrane proteins are diverse in terms of structure, position in the membrane and function.</li> <li>Cholesterol is a component of animal cell membranes.</li> <li>Application: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.</li> <li>Can you draw a diagram of the fluid mosaic model.</li> <li>Can you explain how evidence from electron microscopy led to the proposal of the Davson-Danielli model.</li> <li>Can you outline the evidence which led to the falsification of the Davson-Danielli model and support of the Singer-Nicolson model.</li> </ul> <h3 id="header-2">Mindmaps<small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h3> <p>This diagram summaries the main sections of topic 1.3 about membrane structure.<br> Test if you can draw your own list or concept map from memory.</p> <div id="carousel-74" class="dynamic-gallery carousel slide" data-id="74"><div class="carousel-inner" role="listbox"><div class="item active"><a class="fancy" href="../../../std-galleries/5-74/membrane-structuremmsmalle02.jpg" data-fancybox="gallery-74" title="" data-caption=""><img alt="" src="../../../std-galleries/5-74/membrane-structuremmsmalle02.jpg"></a></div><div class="item "><a class="fancy" href="../../../std-galleries/5-74/membrane-structure-mm-list.png" data-fancybox="gallery-74" title="" data-caption=""><img alt="" src="../../../std-galleries/5-74/membrane-structure-mm-list.png"></a></div></div><a class="left carousel-control" href="#carousel-74" role="button" data-slide="prev"><i class="fa fa-fw fa-chevron-left"></i></a><a class="right carousel-control" href="#carousel-74" role="button" data-slide="next"><i class="fa fa-fw fa-chevron-right"></i></a></div><ol class="std-carousel-indicators"><li data-index="0"><img title="Click to view" src="../../../std-galleries/5-74/membrane-structuremmsmalle02-thumb128.jpg"><li><li data-index="1"><img title="Click to view" src="../../../std-galleries/5-74/membrane-structure-mm-list-thumb128.jpg"><li></li></ol> </div> </div> <div class="panel-footer"> <div> <p>text</p> </div> </div> </div> <div class="panel panel-default"> <div class="panel-heading"><a class="expander pull-right" href="#"><span class="fa fa-plus"></span></a> <div> <p><a id="ESQs" name="ESQs"></a>Exam style questions</p> </div> </div> <div class="panel-body"> <div> <div class="greyBg"> <h3 id="header-3">Skills video tutorial<small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h3> <p>Explaining plasma membrane structure and the structure and function of the molecules in the membrane is an important skill in this topic. This video tutorial explains how to draw a simple 2D diagram of a cell membrane, and label it for an IB Biology exam.</p> <div class="video-embed vimeo"><iframe allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen="" mozallowfullscreen="" webkitallowfullscreen="" height="420" width="100%" src="https://player.vimeo.com/video/281976934?portrait=0"></iframe></div> <script src="../../../api/player.js"></script> <p><a href="https://vimeo.com/281976934">How to draw a membrane diagram in an exam</a> from <a href="https://vimeo.com/user14306679">David Faure</a> on <a href="https://vimeo.com">Vimeo</a>.</p> </div> <div class="panel panel-has-colored-body panel-has-border panel-default"> <div class="panel-heading"><a class="expander pull-right" href="#"><span class="fa fa-plus"></span></a> <div> <p><a id="erq1" name="erq1"></a>Extra exam question about membrane proteins.</p> </div> </div> <div class="panel-body"> <div> <div class="yellowBg"> <p><strong>Describe three functions of membrane proteins. (4)</strong></p> <p>...................................................................................................................................................</p> <p>...................................................................................................................................................</p> <p>...................................................................................................................................................</p> <p>...................................................................................................................................................</p> <p>Hint: Membrane proteins can have several functions. In an answer to a 'describe' question don't just list the functions, describe that function too, giving an example if possible.</p> </div> <p>Click the "+" to reveal a model answer.</p> <button class="btn btn-xs bg-turquoise showhider"><i class="fa fa-fw fa-plus"></i></button><section class="hiddenbox hidden"> <h3 id="header-4">Model answer<small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h3> <div class="yellowBg"> <p><strong>Describe three functions of membrane proteins. (4)</strong></p> <p><span style="color:#FF0000;">Membrane proteins can have the following functions:</span></p> <p><span style="color:#FF0000;">A protein channel is an integral protein that reaches across the membrane. It provides a 'channel' for ions to pass through.</span></p> <p><span style="color:#FF0000;">Peripheral proteins can be enzymes, they catalyse a reaction and are held in place by the membrane.</span></p> <p><span style="color:#FF0000;">Proteins can be hormone binding sites, they have a shape which is specific to the hormone they bind to and they usually communicate a signal into the cytoplasm.</span></p> <p><span style="color:#FF0000;">Other functions could be: Protein pumps, Structural support proteins, or Glycoproteins used in cell identification.</span></p> </div> </section> </div> </div> <div class="panel-footer"> <div> <p>text</p> </div> </div> </div> <div class="panel panel-has-colored-body panel-expandable panel-has-border panel-default"> <div class="panel-heading"><a class="expander pull-right" href="#"><span class="fa fa-plus"></span></a> <div> <p>Extra exam question about phospholipids in membranes - click the + symbol to open it -- ></p> </div> </div> <p> This question requires knowledge of phospholipids and how they form the bilayer structure of the plasma membrane. </p> <div class="panel-body"> <div> <div class="yellowBg"> <p><strong>Explain the role of phospholipids in plasma membrane structure. (5 marks).</strong></p> <p>...................................................................................................................................................</p> <p>...................................................................................................................................................</p> <p>...................................................................................................................................................</p> <p>...................................................................................................................................................</p> <p><em>Examiners hint: for Explain questions, give a description and a reason or cause.</em></p> </div> <p>Click the "+" to reveal a model answer.</p> <button class="btn btn-xs bg-turquoise showhider"><i class="fa fa-fw fa-plus"></i></button><section class="hiddenbox hidden"> <h3 id="header-5">Model answer:<small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h3> <div class="yellowBg"> <p><strong>Explain the role of phospholipids in plasma membrane structure. (5 marks).</strong></p> <ul> <li><span style="color:#FF0000;">Phospholipids are amphipathic molecules with hydrophobic and hydrophilic parts.</span></li> <li><span style="color:#FF0000;">The phospholipid head of the molecule is hydrophilic, the fatty acid tail of the molecule is hydrophobic.</span></li> <li><span style="color:#FF0000;">In water, phospholipids form a bilayer, with the fatty acid tails facing each other in the centre of the bilayer.</span></li> <li><img alt="" src="../../images/01_cells/bilayer_labelled.png" style="width: 330px; height: 147px;"></li> <li><span style="color:#FF0000;">The bilayer is held together by hydrophobic interactions between fatty acid tails.</span></li> <li><span style="color:#FF0000;">This association means that the plasma membrane can reseal and reassemble, making it's structure 'fluid'.</span></li> <li><span style="color:#FF0000;">Proteins assemble in the bilayer based on the position of hydrophilic and hydrophobic amino acids in their structures.</span></li> <li><span style="color:#FF0000;">They can move within the membrane but remain within the membrane g</span><span style="color:#FF0000;">iving the fluid mosaic model of membrane structure.</span></li> </ul> <p><em>You can include a fully labelled diagram to help with your explanation</em></p> </div> <p><span style="color:#0000FF;"></span></p> </section> </div> </div> <div class="panel-footer"> <div> <p>text</p> </div> </div> </div> </div> </div> <div class="panel-footer"> <div> <p>text</p> </div> </div> </div> <div class="panel panel-green"> <div class="panel-heading"><a class="expander pull-right" href="#"><span class="fa fa-plus"></span></a> <div> <p>Test yourself</p> </div> </div> <div class="panel-body"> <div> <h3 id="header-6">Multiple choice quiz<small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h3> <p>This quiz contains a set of multiple choice questions covering the membrane structure topic. Explanations of each answer are displayed after you click to check the answer(s).</p> <br><a class="btn btn-primary btn-block text-center" data-toggle="modal" href="#029cac11"><i class="fa fa-play"></i> START QUIZ!</a><div class="modal fade modal-slide-quiz" id="029cac11"> <div class="modal-dialog" style="width: 95vw; max-width: 960px"> <div class="modal-content"> <div class="modal-header slide-quiz-title"> <h4 id="header-7"> 1.3 Membrane structure <strong class="q-number pull-right"> <span class="counter">1</span>/<span class="total">1</span> </strong> <small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h4> </div> <div class="modal-body p-xs-3"> <div class="slide-quiz" data-stats="5-201-607" style="opacity: 0"> <div class="exercise shadow-bottom"><div class="q-question"><p>Which property of phospholipid molecules describes the fact that they have both hydrophobic and hydrophilic parts?</p></div><div class="q-answer"><p><label class="radio"><input type="radio"> Amphoteric properties</label></p><p><label class="radio"><input type="radio"> Lipid properties</label></p><p><label class="radio"><input class="c" type="radio"> Amphipathic properties</label></p><p><label class="radio"><input type="radio"> Phosphate properties</label></p></div><div class="q-explanation"><p>Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules. The hydrophobic tails attract each other and the hydrophilic phosphates are attracted to the water.</p><p>Amphoteric substances may behave either as an acid or a base depending on the environment. Amino acids are said to be amphoteric because they both have a basic group (amine: NH2/NH3+) and an acid group (carboxylic acid) but this doesn't help them form bilayers.</p></div><div class="slide-q-actions"><button class="btn btn-default btn-sm btn-xs-block text-xs-center check"><i class="fa fa-check-square-o"></i> Check</button></div></div><div class="exercise shadow-bottom"><div class="q-question"><p>Which of the following is true of peripheral proteins in cell membranes?</p></div><div class="q-answer"><p><label class="radio"><input type="radio"> They are found only in the lipid part of of the membrane.</label></p><p><label class="radio"><input type="radio"> The are found embedded in the membrane, partly in the cytoplasm and partly outside the cell.</label></p><p><label class="radio"><input class="c" type="radio"> They are found attached to the membrane, but on its surface.</label></p><p><label class="radio"><input type="radio"> They are found on the surface of the membrane but they are not attached to it. </label></p></div><div class="q-explanation"><p>Membrane proteins are diverse in terms of structure, position in the membrane and function.<br>Peripheral proteins are attached to the membrane but found on its surface.</p></div><div class="slide-q-actions"><button class="btn btn-default btn-sm btn-xs-block text-xs-center check"><i class="fa fa-check-square-o"></i> Check</button></div></div><div class="exercise shadow-bottom"><div class="q-question"><p>What effect does reducing the amount of cholesterol in a cell membrane have on its properties?</p></div><div class="q-answer"><p><label class="radio"><input class="c" type="radio"> It would increase membrane fluidity and permeability to some solutes.</label></p><p><label class="radio"><input type="radio"> It would reduce membrane fluidity but has no effect on permeability.</label></p><p><label class="radio"><input type="radio"> It would reduce membrane fluidity and permeability to some solutes.</label></p><p><label class="radio"><input type="radio"> It would increase membrane fluidity but has no effect on permeability.</label></p></div><div class="q-explanation"><p>Cholesterol is a component of animal cell membranes. Application: Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes.</p></div><div class="slide-q-actions"><button class="btn btn-default btn-sm btn-xs-block text-xs-center check"><i class="fa fa-check-square-o"></i> Check</button></div></div><div class="exercise shadow-bottom"><div class="q-question"><p><img alt="" src="../../images/01_cells/cell-membrane-tem.jpeg" style="width: 200px; height: 196px; float: right;">The photograph is from an electron microscope image of a membranes.<br>Parallel dark lines are clearly seen.<br>In electron micrography, heavy metal stains are often used to enhance contrast. DNA and Proteins often show as dark areas because these molecules can attach to the stain.</p><p>Which of the following interpretations is most similar to the proposal of the Daveson-Danielli model of membranes?</p><hr class="hidden-separator"></div><div class="q-answer"><p><label class="radio"><input type="radio"> The two dark lines are layers of phospholipid.</label></p><p><label class="radio"><input type="radio"> The pattern of the lines indicates a helical protein structure forming part of the membrane.</label></p><p><label class="radio"><input class="c" type="radio"> The two dark lines are layers of protein which surround the phospholipids.</label></p><p><label class="radio"><input type="radio"> The dark lines show protein layer inside the phospholipids.</label></p></div><div class="q-explanation"> <p>Students are expected to know how to use evidence from electron microscopy to support an idea about membranes. One illustration of this is the proposal of the Davson-Danielli model.</p><p>Further evidence lead to the falsification of the Davson-Danielli model and the proposal of the fluid mozaic model.</p></div><div class="slide-q-actions"><button class="btn btn-default btn-sm btn-xs-block text-xs-center check"><i class="fa fa-check-square-o"></i> Check</button></div></div><div class="exercise shadow-bottom"><div class="q-question"><p>The illustration shown below is of a protein (green) attached to a membrane.</p><p><img alt="" src="../../images/01_cells/membrane-protein-1.jpeg" style="width: 350px; height: 185px;"></p><p>What is the most likely function of this membrane protein?</p></div><div class="q-answer"><p><label class="radio"><input type="radio"> It is a molecule carrying oxygen.</label></p><p><label class="radio"><input type="radio"> It is an enzyme </label></p><p><label class="radio"><input class="c" type="radio"> It carries signals from outside the cell to the cytoplasm.</label></p><p><label class="radio"><input type="radio"> It is a structural protein.</label></p></div><div class="q-explanation"><p>This protein is found in the human liver, where the hormone adrenaline indirectly stimulates it to mobilise stored energy inside liver cells in the "fight or flight" response. </p><p>The fact that it is a transmembrane protein is essential for this function.</p><p>It is interesting to note that this protein is also secreted by <em>Anthrax</em> bacteria as a toxin.<br>It upsets the metabolism of host cells when it enters them.</p></div><div class="slide-q-actions"><button class="btn btn-default btn-sm btn-xs-block text-xs-center check"><i class="fa fa-check-square-o"></i> Check</button></div></div><div class="exercise shadow-bottom"><div class="q-question"><p>What is the name given to the type of molecule found in membranes which is made from carbohydrate and protein.</p></div><div class="q-answer"><p><label class="radio"> <input type="radio"> <span><span class="scayt-misspell-word" data-scayt-word="Starchamine" data-wsc-lang="en_GB">Starchamine</span></span></label> </p><p><label class="radio"> <input type="radio"> <span>Cholesterol</span></label> </p><p><label class="radio"> <input class="c" type="radio"> <span>Glycoprotein</span></label> </p><p><label class="radio"> <input type="radio"> <span><span class="scayt-misspell-word" data-scayt-word="Carboprotein" data-wsc-lang="en_GB">Carboprotein</span></span></label> </p></div><div class="q-explanation"><p>Glycoproteins have many functions in the human body, many involve interactions between cells.</p><p>Interestingly the hormones, FSH and LH are also glycoproteins.</p></div><div class="slide-q-actions"><button class="btn btn-default btn-sm btn-xs-block text-xs-center check"><i class="fa fa-check-square-o"></i> Check</button></div></div> </div> </div> <div class="modal-footer slide-quiz-actions"> <div class=""> <div class="pull-left pull-xs-none mb-xs-3"> <button class="btn btn-default d-xs-none btn-prev"> <i class="fa fa-arrow-left"></i> Prev </button> </div> <div class="pull-right pull-xs-none"> <button class="btn btn-success btn-xs-block text-xs-center btn-results" style="display: none"> <i class="fa fa-bar-chart"></i> Check Results </button> <button class="btn btn-default d-xs-none btn-next"> Next <i class="fa fa-arrow-right"></i> </button> <button class="btn btn-default btn-xs-block text-xs-center btn-close" data-dismiss="modal" style="display: none"> Close </button> </div> </div> </div> </div> </div></div> <hr> <h3 id="header-8">Drag and drop activities<small class="toc-back-button"><a href="#" class="scroll-to" data-target="toc-1675505948" title="Back to table of contents"><i class="fa fa-chevron-circle-up gray"></i></a></small></h3> </div> </div> </div> <div class="tib-quiz" data-stats="5-825-607"><p>Test your construction of biological explanations using the drag and drop questions below.</p><p><strong>The structure of cholesterol and its role in membrane structure.</strong></p><p>Drag and drop the correct term into the gap to describe the structure and role of cholesterol in the plasma membrane.</p><p><img alt="" src="../../images/richard/1.3-cholesterol_molecule_ball.png" style="width: 180px; height: 90px;"></p><div class="label label-default q-number">1</div><div class="exercise shadow-bottom"><div class="q-question"><p> </p><p class="gap-drop"> <span class="q-text-draggable draggable" draggable="true">fluid</span> <span class="q-text-draggable draggable" draggable="true">rigidity</span> <span class="q-text-draggable draggable" draggable="true">rigid</span> <span class="q-text-draggable draggable" draggable="true">hydrophilic</span> <span class="q-text-draggable draggable" draggable="true">water-soluble</span> <span class="q-text-draggable draggable" draggable="true">permeability</span> <span class="q-text-draggable draggable" draggable="true">anchoring</span> <span class="q-text-draggable draggable" draggable="true">amphipathic</span> <span class="q-text-draggable draggable" draggable="true">hydrophobic tails </span> <span class="q-text-draggable draggable" draggable="true">vesicles</span> </p></div><div class="q-answer"><p>Cholesterol is an <input type="text" style="height: auto;" data-c="amphipathic"> <span class="review"></span> lipid which gives <input type="text" style="height: auto;" data-c="rigidity"> <span class="review"></span> to the cell membrane by binding in-between the <input type="text" style="height: auto;" data-c="hydrophobic tails "> <span class="review"></span> of the phospholipid molecules in the bilayer close to the <input type="text" style="height: auto;" data-c="hydrophilic"> <span class="review"></span> heads of the phospholipids.</p><p>This allows the membrane to be <input type="text" style="height: auto;" data-c="fluid"> <span class="review"></span> but to retain a definite structure such as in the formation of <input type="text" style="height: auto;" data-c="vesicles"> <span class="review"></span> .</p><p>The more cholesterol present, the more <input type="text" style="height: auto;" data-c="rigid"> <span class="review"></span> the membrane.</p><p>As it is a lipid, it also reduces <input type="text" style="height: auto;" data-c="permeability"> <span class="review"></span> to <input type="text" style="height: auto;" data-c="water-soluble"> <span class="review"></span> molecules.</p><p>It aids in <input type="text" style="height: auto;" data-c="anchoring"> <span class="review"></span> proteins to the bilayer.</p></div><div class="q-explanation"><p><em>Explanation/Examiner hint. Structure and role means both must be in your response to gain full marks. </em></p></div><div class="actions"><span class="score" data-score="0"></span><button class="btn btn-default btn-sm btn-xs-block text-xs-center check"><i class="fa fa-check-square-o"></i> Check</button></div></div><div class="totals"><span class="score"></span><button class="btn btn-success btn-block text-center check-total"><i class="fa fa-check-square-o"></i> Check</button></div></div><hr> <div class="panel panel-fucsia"> <div class="panel-heading"> <div> <p>Just for fun</p> </div> </div> <div class="panel-body"> <div> <p>If you want to review key terminology and have some fun with your revision try this. It will help you remember the terms through repetition. <a href="http://quizlet.com/51855022/match" target="_blank">Membrane structure card match game.</a></p> <ul> </ul> <p style="text-align: center"><iframe height="500" src="https://quizlet.com/51855022/match/embed" style="border:0" width="100%"></iframe></p> <p>Alternatively this choice of Arcade games will help you to practise the basics while having fun. <a href="http://www.classtools.net/arcade/201807_SiDa2c" target="_blank">Arcade game "Membrane structure".</a></p> <p align="center"><iframe frameborder="0" height="250" scrolling="no" src="//www.classtools.net/widg/201807_SiDa2c" width="570"></iframe></p> </div> </div> <div class="panel-footer"> <div> <p>text</p> </div> </div> </div> <ul> </ul> <div class="page-container panel-self-assessment" data-id="607"> <div class="panel-heading">MY PROGRESS</div> <div class="panel-body understanding-rate"> <div class="msg"></div> <label class="label-lg">Self-assessment</label><p>How much of 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