Name: how biomolecules hold their shape
Uploaded: 2020-11-23T11:47:33.000Z
Duration: 2 min 35 s
Channel: JoVE

K12 Standards

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

High School

Chemistry

Matter and Its Interactions

C-PS1-3.

Noncovalent Attractions in Biomolecules

Les liaisons covalentes se forment quand des paires d'électrons sont échangées lors d'interactions entre des atomes. Ces liaisons fortes nécessitent une grande quantité d'énergie pour être rompues. Tandis que les liaisons covalentes sont des forces intramoléculaires qui connectent les atomes en molécules, les attractions intermoléculaires et non-covalentes stabilisent les groupes d'atomes entre les molécules ou dans différentes parties d'une plus grande molécule.Bien qu'individuellement faible, de nombreuses interactions non-covalentes ensemble peuvent maintenir des molécules associées pour une période prolongée. Quatre grands types d'attractions non-covalentes se produisent dans les systèmes biologiques-Interactions ioniques, liaisons hydrogène, forces de Van der Waals, et interactions hydrophobes. Les interactions ioniques se produisent entre des ions à charge opposée.Le squelette de l'ADN a de nombreux groupes phosphate proches les uns des autres et chargés négativement. Pour stabiliser la molécule, les cations, tels que le magnésium, interagissent avec les groupes phosphate, neutralisant la charge nette de l'ADN. Une liaison hydrogène se forme quand un atome d'hydrogène qui est lié de façon covalente à un atome hautement électronégatif, comme l'oxygène ou l'azote, interagit avec la seule paire d'électrons d'un autre atome électronégatif.Dans l'ADN, les brins complémentaires sont appariés ensemble par liaisons hydrogène. Une base d'un brin partage ses hydrogènes liés de façon covalente avec des atomes d'azote ou d'oxygène sur une autre base du brin opposé. Les interactions de Van der Waals se produisent lorsque deux molécules s'approchent l'une de l'autre.Ces forces attractives non-spécifiques résultent de dipôles temporaires générés par le mouvement rapide des électrons à travers la molécule. Cependant, lorsque les molécules se rapprochent trop, la répulsion électrostatique renverse les interractions de Van der Waals. Enfin, les interactions hydrophobes sont une association forcée de groupes hydrophobes en raison à la répulsion des molécules d'eau.Dans un environnement aqueux, les parties hydrophobes des molécules lipidiques ne peuvent pas perturber facilement la liaison hydrogène entre les molécules d'eau. L'interaction entre les molécules d'eau est plus forte que l'interaction entre les molécules lipidiques et aqueuses. Donc les parties hydrophobes des lipides s'associent, causant l'agrégation des lipides.

<ol>
	<li>Frieden, Earl. « Interactions non covalentes : clé de la flexibilité et de la spécificité biologiques. » Journal de l’éducation chimique 52, n° 12 (1975) : 754.</li>
	<li>Camilloni, Carlo, Daniela Bonetti, Angela Morrone, Rajanish Giri, Christopher M. Dobson, Maurizio Brunori, Stefano Gianni et Michele Vendruscolo. « Vers une biologie structurale de l’effet hydrophobe dans le repliement des protéines ». Rapports scientifiques 6, n° 1 (2016) : 1-9.</li>
	<li>Weiss, Manfred S., Maria Brandl, Jürgen Sühnel, Debnath Pal et Rolf Hilgenfeld. « Plus de liaisons hydrogène pour le biologiste (structurel) ». Tendances en sciences biochimiques 26, n° 9 (2001) : 521-523.</li>
</ol>

attractions non covalentes dans les biomolécules

Les attractions non covalentes sont des associations au sein et entre les molécules qui influencent la forme et la stabilité structurelle des complexes. Ces interactions diffèrent des liaisons covalentes dans la mesure où elles n'impliquent pas de partage d'électrons.

Les quatre types d'interactions non covalentes sont: Les liaisons hydrogène, les forces de Van der Waals, les liaisons ioniques et les interactions hydrophobes.

La liaison hydrogène résulte de l’attraction électrostatique d’un atome d’hydrogène lié de manière covalente à un atome fortement électronégatif comme l’oxygène, l’azote ou le fluor par un autre atome électronégatif. L’atome d’hydrogène développe une charge partielle positive lorsque l’atome électronégatif auquel il est lié attire le nuage électronique à proximité de lui. En conséquence, une faible interaction se produit entre la charge δ+ de l’hydrogène et la charge δ– de l’atome électronégatif voisin. Ce type d'interaction se forme régulièrement entre les molécules d'eau. Les liaisons hydrogène indépendantes se rompent facilement ; cependant, elles sont présentes en grand nombre dans l’eau et les polymères organiques, créant ainsi une force combinée importante.

Un deuxième type d’interaction appelé van der Waals est provoqué par des attractions temporaires entre des régions riches en électrons et les régions pauvres en électrons de deux ou plusieurs atomes (ou molécules) proches les uns des autres. Ces interactions peuvent contribuer aux structures tridimensionnelles des protéines essentielles à leur fonction.

Un autre type d’interaction est la liaison ionique qui se produit entre des ions de charges opposées. Dans les systèmes biologiques, les interactions ioniques résultant d’ions de charges opposées peuvent également aider à stabiliser la structure des biomolécules. Les ions métalliques, tels que le magnésium, interagissent avec des biomolécules chargées négativement telles que l'ADN. L'ion magnésium se lie aux groupes phosphate négatifs, neutralisant ainsi la charge et aidant à emballer le long polymère d'ADN dans des structures solénoïdes ou toroïdes.

Enfin, l’effet hydrophobe est une interaction non covalente dans laquelle les molécules hydrophobes s’agrègent pour minimiser le contact avec l’eau dans un environnement aqueux. En conséquence, les régions hydrophobes d’un polypeptide sont enfouies dans la structure lors du repliement des protéines.

Attractions non covalentes dans les biomolécules

Les attractions non covalentes sont des associations à l’intérieur et entre les molécules qui influencent la forme et la stabilité structurelle des complexes. Ces interactions ...

Education

Enseignement

JoVE Core

Molecular Biology

Biologie moléculaire

Unit 1

Unité 1

Biochemistry of the Cell

Biochimie de la cellule

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

how biomolecules hold their shape

Biomolecules hold their shape through noncovalent attractions. These interactions occur within and between molecules and help control the structure and stability of complexes. They are different from covalent bonds because they do not involve sharing electrons.

Four main noncovalent interactions are important in biology: hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions. Hydrogen bonds form when a hydrogen atom is covalently bonded to a strongly electronegative atom, such as oxygen, nitrogen, or fluorine. That atom pulls the electron cloud closer, so the hydrogen gains a partial positive charge. The hydrogen is then attracted to a nearby electronegative atom with a partial negative charge.

Hydrogen bonding occurs regularly between water molecules. A single hydrogen bond is easy to break, but many hydrogen bonds together can create a strong combined force. This is also true in organic polymers, where many weak bonds add up to a major effect.

Van der Waals forces come from temporary attractions between electron-rich and electron-poor regions of atoms or molecules that are close together. These weak interactions can help proteins form their three-dimensional shapes, which are essential for protein function. Ionic bonding occurs between oppositely charged ions, and these ionic interactions can also stabilize biomolecular structure.

Metal ions can also play a structural role. In DNA, magnesium ions interact with negatively charged phosphate groups. This binding helps neutralize charge and assists in packing the long DNA polymer into solenoid or toroid structures. Another important force is the hydrophobic effect. In water, hydrophobic molecules cluster together to avoid contact with water, and hydrophobic regions of a polypeptide become buried during protein folding.

How Biomolecules Hold Their Shape

the periodic table and organismal elements

the-periodic-table-and-organismal-elements

Element Groups in Living Things

Living things are built from elements found on the periodic table. This page focuses on the elements that make up organisms and how they are grouped in biology. These organismal elements are usually divided into major, minor, and trace categories. Major elements make up most of the mass of living matter. Minor elements are needed in smaller amounts. Trace elements are present in very small amounts but still play important roles. The periodic table helps show where these elements fit and how...

functional groups

Functional Groups in Organic Molecules

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polymers

Polymer Structures and Uses

Polymers are large molecules built from repeating smaller units called monomers. Their long-chain structure gives them many different properties and makes them useful in everyday materials. Polymers can form in two main ways. In addition polymerization, monomers join together without losing any atoms. In condensation polymerization, monomers link while a small molecule is released. These two pathways help explain how many common plastics and related materials are made. The structure of a...

what are lipids?

Lipids in Cells: Fats and Membranes

Lipids are a group of biomolecules found in living things. They are known for their role in energy storage and in building cell membranes. This makes them important in many parts of biology. Fats are one common type of lipid. Other lipids include phospholipids and steroids. Each group has a different structure and a different job in the body. Phospholipids are especially important because they help form cell membranes. Steroids also belong to the lipid group, and they have their own distinct...

structure of lipids

Types of Lipids and Their Structure

Lipids are a major group of biological molecules, and their structure helps explain their different forms. Many lipids are built from fatty acids, which are long hydrocarbon chains with a carboxyl group. The carbon chain is hydrophobic, meaning it does not mix well with water, while the carboxyl group is the acidic end. Triglycerides are one common lipid type. They consist of a glycerol molecule joined to three fatty acid chains. Saturated triglycerides have fatty acids with only single...

chemistry of carbohydrates

Carbohydrate Structures and Types

Carbohydrates are biomolecules built from carbon, hydrogen, and oxygen. Their chemistry helps explain how simple sugars join together and how larger carbohydrate molecules form. The smallest carbohydrates are monosaccharides, or single sugar units. These can link to make disaccharides, which contain two sugar units, and polysaccharides, which are long chains of many sugar units. Carbohydrates play an important role in biology because they are part of the structures and processes found in...

nucleic acids

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Nucleic acids carry genetic information in cells. They include DNA and RNA, which are made from nucleotide building blocks. These molecules store, copy, and help use the instructions needed for life. DNA is the main long-term storage molecule for genetic information. RNA helps carry and use that information in cells. Together, these nucleic acids connect the code in a cell to the proteins it can make.

intermolecular forces

Forces Between Molecules

Forces between molecules help explain why matter behaves the way it does. These intermolecular attractions act between separate molecules, not within a single molecule. They are often much weaker than the bonds that hold atoms together inside a molecule, but they still affect many properties of liquids and solids. Several common types of intermolecular forces are covered in this topic. These include dipole-dipole forces, hydrogen bonding, ion-dipole forces, and van der Waals forces. Van der...

noncovalent attractions in biomolecules

Biomolecules hold their shape through noncovalent attractions. These interactions occur within and between molecules and help control the structure and stability of complexes. They are different from covalent bonds because they do not involve sharing electrons. Four main noncovalent interactions are important in biology: hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic interactions. Hydrogen bonds form when a hydrogen atom is covalently bonded to a strongly electronegative...

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ATP Hydrolysis and Energy Release

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key terms and concepts

Explore hydrogen bonds, van der Waals forces, ionic bonds, and hydrophobic effects, and see how they help stabilize proteins and DNA in cells.

How Biomolecules Hold Their Shape | JoVE K12

molecular biology

JoVE Core Biologie Moléculaire illustre les processus moléculaires au sein de la cellule grâce à des leçons vidéos claires et concises. Les applications de ces concepts sont ensuite démontrées grâce à des expériences concrètes en laboratoire.

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C-PS1-6

How Biomolecules Hold Their Shape

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