<p>Ionic and covalent bonds between <a data-lesson="the-building-blocks-of-life" data-subject="biology" data-tutorial="chemical-foundation-of-life" href="https://app.ulearngo.com/biology/chemical-foundation-of-life/the-building-blocks-of-life">elements</a> require energy to break. Ionic bonds are not as strong as covalent, which determines their <a data-lesson="summarizing-behavioral-biology" data-subject="biology" data-tutorial="population-community-ecology" href="https://app.ulearngo.com/biology/population-community-ecology/summarizing-behavioral-biology">behavior</a> in biological systems. However, not all bonds are ionic or covalent bonds. Weaker bonds can also form between molecules.</p>
<p>Two weak bonds that occur frequently are hydrogen bonds and van der Waals interactions. Without these two types of bonds, <a href="https://app.ulearngo.com/tutorials/introducing-study-of-life/what-is-life">life</a> as we know it would not exist. Hydrogen bonds provide many of the critical, life-sustaining properties of water and also stabilize the structures of <a data-lesson="proteins-2" data-subject="biology" data-tutorial="biology-foundations" href="https://app.ulearngo.com/biology/biology-foundations/proteins-2">proteins</a> and DNA, the building block of cells.</p>
<h2>Hydrogen Bond</h2>
<p>When polar covalent bonds containing hydrogen form, the hydrogen in that bond has a slightly positive charge. This is because hydrogen’s electron is pulled more strongly toward the other element and away from the hydrogen. Because the hydrogen is slightly positive, it is attracted to neighboring negative charges. When this happens, a weak interaction occurs between the <em data-effect="italics">δ</em><sup>+</sup>of the hydrogen from one molecule and the <em data-effect="italics">δ</em><sup>–</sup> charge on the more electronegative <a data-lesson="chemical-reactions-molecules" data-subject="biology" data-tutorial="chemical-foundation-of-life" href="https://app.ulearngo.com/biology/chemical-foundation-of-life/chemical-reactions-molecules">atoms</a> of another molecule, usually <a data-lesson="transport-of-oxygen-in-the-blood" data-subject="biology" data-tutorial="respiratory-system" href="https://app.ulearngo.com/biology/respiratory-system/transport-of-oxygen-in-the-blood">oxygen</a> or nitrogen, or within the same molecule. This interaction is called a <strong>hydrogen bond</strong>.</p>
<div class="wp-caption alignnone" id="attachment_95257" style="width: 722px"><a href="https://data.ulearngo.com/assets/2bde0ed9-0b3d-4c71-bdfc-14ef586af94a"><img alt="hydrogen-bond" class="size-full wp-image-95257" height="599" src="https://data.ulearngo.com/assets/2bde0ed9-0b3d-4c71-bdfc-14ef586af94a" width="722"/></a><p class="wp-caption-text">Simulation of hydrogen bonds in liquid water. Image Attribution: Thomas Splettstoesser via Wikimedia Commons (<a href="https://creativecommons.org/licenses/by-sa/3.0/deed.en">CC BY-SA 3.0</a> license)</p></div>
<p>This type of bond is common and occurs regularly between water molecules. Individual hydrogen bonds are weak and break easily; however, they occur in very large numbers in water and in organic polymers, creating a major force in combination. Hydrogen bonds are also responsible for zipping together the <a href="https://app.ulearngo.com/tutorials/introducing-genetics/dna">DNA</a> double helix.</p>
<h2>Van Der Waals Interactions</h2>
<p>Like hydrogen bonds, <strong>van der Waals interactions</strong> are weak attractions or interactions between molecules. Van der Waals attractions can occur between any two or more molecules and are dependent on slight fluctuations of the electron densities, which are not always symmetrical around an atom.</p>
<p>For these attractions to happen, the molecules need to be very close to one another. These bonds—along with ionic, covalent, and hydrogen bonds—contribute to the three-dimensional structure of the proteins in our <a data-lesson="prokaryotic-and-eukaryotic-cells" data-subject="biology" data-tutorial="cell-biology" href="https://app.ulearngo.com/biology/cell-biology/prokaryotic-and-eukaryotic-cells">cells</a> that is necessary for their proper function.</p>

ad260561-7f24-4cf8-a3f2-b129f5e47c91

Hydrogen Bonds

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.

Biology

Discover the basic concepts of chemistry that serve as the foundation of life, including the structure of atoms and the periodic table, as well as the role of water, carbon and organic compounds in living organisms.


Hydrogen Bonds

Track Your Learning Progress