<h2>Facilitated Diffusion</h2>
<p>Facilitated diffusion is a special form of diffusion which allows rapid exchange of specific substances. Particles are taken up by carrier <a data-lesson="proteins-2" data-subject="biology" data-tutorial="biology-foundations" href="https://app.ulearngo.com/biology/biology-foundations/proteins-2">proteins</a> which change their shape as a result. The change in shape causes the particles to be released on the other side of the membrane.</p>
<p>Facilitated diffusion can only occur across living, biological membranes which contain the carrier proteins. A substance is transported via a carrier protein from a region of high concentration to a region of low concentration until it is randomly distributed. Therefore movement is <i class="emphasis">down a concentration gradient</i>.</p>
<div class="wp-caption alignnone" id="attachment_100104" style="width: 535px"><a href="https://data.ulearngo.com/assets/22d4e80c-46c9-44d3-9bc1-ad946be879e9"><img alt="facilitated-diffusion" class="size-full wp-image-100104" height="234" src="https://data.ulearngo.com/assets/22d4e80c-46c9-44d3-9bc1-ad946be879e9" width="535"/></a><p class="wp-caption-text">Image credit: Siyavula</p></div>
<p>Examples of substances moved via facilitated diffusion include all polar <a data-lesson="first-organic-molecules" data-subject="biology" data-tutorial="evolution-overview" href="https://app.ulearngo.com/biology/evolution-overview/first-organic-molecules">molecules</a> such as <a data-lesson="connections-of-other-sugars-to-glucose-metabolism" data-subject="biology" data-tutorial="cellular-respiration" href="https://app.ulearngo.com/biology/cellular-respiration/connections-of-other-sugars-to-glucose-metabolism">glucose</a> or amino acids.</p>
<h2>Active Transport</h2>
<p>Active transport is the movement of substances <i class="emphasis">against</i> a concentration gradient, from a region of <i class="emphasis">low concentration</i> to <i class="emphasis">high concentration</i> using an input of energy. In biological systems, the form in which this energy occurs is <em class="emphasis">adenosine triphosphate (ATP)</em>. The process transports substances through a <a data-lesson="membrane-proteins" data-subject="biology" data-tutorial="cell-biology" href="https://app.ulearngo.com/biology/cell-biology/membrane-proteins">membrane</a> protein. The movement of substances is selective via the carrier proteins and can occur into or out of the cell.</p>
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<h3 class="note-header"><span class="cnx_label">Fact:</span></h3>
<p class="para">ATP and ADP are molecules involved with moving energy within cells. You do not need to know these names in full and will learn more about them later.</p>
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<div class="wp-caption alignnone" id="attachment_100105" style="width: 535px"><a href="https://data.ulearngo.com/assets/18732cd2-e536-487e-af22-4fde36dc10f7"><img alt="active-transport" class="size-full wp-image-100105" height="240" src="https://data.ulearngo.com/assets/18732cd2-e536-487e-af22-4fde36dc10f7" width="535"/></a><p class="wp-caption-text">Image credit: Siyavula</p></div>
<p>Examples of substances moved include <a data-lesson="mineralocorticoids" data-subject="biology" data-tutorial="excretory-system" href="https://app.ulearngo.com/biology/excretory-system/mineralocorticoids">sodium</a> and potassium ions as shown in the figure above.</p>
<h2>Video: Cell Membranes and Cell Transport</h2>
<p>The <a href="http://www.amoebasisters.com/">Amoeba Sisters</a> video below explores the types of passive and active cell transport. </p>
<p><iframe allowfullscreen="allowfullscreen" frameborder="0" height="360" src="https://www.youtube.com/embed/Ptmlvtei8hw?rel=0&amp;modestbranding=1&amp;cc_lang_pref=en&amp;cc_load_policy=1" width="640"></iframe></p>

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Facilitated Diffusion and Active Transport

Biology studies life and living organisms. Biology can be divided into different sections that cover the morphology, physiology, anatomy, behavior, and so on of living organisms.

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Facilitated Diffusion and Active Transport

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