Name: biomolecule interactions without covalent bonds
Uploaded: 2023-04-30T18:28:47.000Z
Duration: 2 min 35 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.1

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 ...

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biomolecule interactions without covalent bonds

Biomolecules often stay together through noncovalent attractions instead of covalent bonds. These weaker interactions help molecules recognize each other and form structures needed for life.

The main noncovalent attractions are hydrogen bonds, electrostatic interactions, van der Waals forces, and hydrophobic interactions. Each one works in a different way, but all of them can influence how biomolecules fold, bind, and behave in cells.

Hydrogen bonds form when a hydrogen atom is attracted to another atom with a partial negative charge. Electrostatic interactions occur between charged groups, while van der Waals forces are very short-range attractions between nearby atoms. Hydrophobic interactions help nonpolar parts of molecules cluster together in water.

Together, these attractions are essential in biomolecules such as proteins, DNA, and other cellular molecules. They are not as strong as covalent bonds, but their combined effect is powerful and helps maintain biological structure and function.

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SC.912.L.18.7

A. All living things are composed of four basic categories of macromolecules and share the same basic needs for life.

B. Living organisms acquire the energy they need for life processes through various metabolic pathways (primarily photosynthesis and cellular respiration).

C. Chemical reactions in living things follow basic rules of chemistry and are usually regulated by enzymes.

D. The unique chemical properties of carbon and water make life on Earth possible.

Biomolecule Interactions Without Covalent Bonds

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