Name: cell energy loss and entropy
Uploaded: 2023-04-30T10:41:06.000Z
Duration: 1 min 22 s
Channel: JoVE
Description: Cell energy loss and entropy explain why living things need constant energy input. Cells obtain energy, transform it, and use it to do work, but these transfers are never completely efficient. In each transfer, some energy is lost in a form that cannot be used. In many cases, that lost energy is heat energy.

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Energy

HS-PS3-1

Entropy within the Cell

Les cellules vivantes suivent la deuxième loi de la thermodynamique, qui stipule que les systèmes ont tendance à passer d’états ordonnés à faible entropie à des états désordonnés à entropie élevée sans apport extérieur.
Par exemple, le transport passif de l’oxygène concentré des poumons vers le sang moins oxygéné disperse les molécules d’oxygène, augmentant ainsi l’entropie du système.
Les cellules tirent leur énergie de la dégradation de molécules telles que le glucose. Les sous-produits de la réaction – dioxyde de carbone, eau et chaleur – sont libérés dans l’environnement, augmentant son entropie.
La survie cellulaire dépend de systèmes hautement ordonnés tels que l’ADN et les protéines. La formation de ces structures ordonnées provoque une diminution de l’entropie du système, qui doit être accompagnée d’une augmentation égale ou supérieure de l’entropie de l’environnement.
Les brins d’ADN simples sont désordonnés et leur entropie diminue lorsqu’ils se renouvellent en une structure ordonnée à double hélice.
Dans le même temps, l’énergie est libérée dans l’environnement lors de la formation d’une double hélice. Cette énergie rend l’environnement plus désordonné et augmente son entropie.

entropie dans la cellule

Les tâches principales d'une cellule vivante consistant à obtenir, transformer et utiliser l'énergie pour effectuer son travail peuvent sembler simples. Cependant, la deuxième loi de la thermodynamique explique pourquoi ces tâches sont plus difficiles qu’il n’y paraît. Aucun des transferts d’énergie dans l’univers n’est totalement efficace. Lors de chaque transfert d’énergie, une certaine quantité d’énergie est perdue sous une forme inutilisable. Dans la plupart des cas, cette forme est de l’énergie thermique. Thermodynamiquement, l'énergie thermique est définie comme l'énergie transférée d'un système à un autre sans travail. Par exemple, une partie de l’énergie est perdue sous forme d’énergie thermique lors des réactions métaboliques cellulaires.

Un concept important dans les systèmes physiques est celui d’ordre et de désordre. Plus un système perd d’énergie dans son environnement, moins le système est ordonné et aléatoire. Les scientifiques appellent la mesure du caractère aléatoire ou du désordre au sein d’un système l’entropie. Une entropie élevée signifie un désordre élevé et une faible énergie. Les molécules et les réactions chimiques ont également une entropie variable. Par exemple, l’entropie augmente à mesure que des molécules en forte concentration en un seul endroit se diffusent et se propagent.

Les êtres vivants sont hautement ordonnés, nécessitant un apport d’énergie constant pour être maintenus dans un état de faible entropie. À mesure que les systèmes vivants absorbent des molécules stockant de l’énergie et les transforment par des réactions chimiques, ils perdent une certaine quantité d’énergie utilisable au cours du processus, car aucune réaction n’est complètement efficace. Ils produisent également des déchets et des sous-produits qui ne constituent pas des sources d’énergie utiles. Ce processus augmente l'entropie de l'environnement du système. Puisque tous les transferts d’énergie entraînent la perte d’une partie de l’énergie utilisable, la deuxième loi de la thermodynamique stipule que chaque transfert ou transformation d’énergie augmente l’entropie de l’univers. Même si les êtres vivants sont hautement ordonnés et maintiennent un état de faible entropie, l’entropie totale de l’univers augmente constamment en raison de la perte d’énergie utilisable à chaque transfert d’énergie qui se produit. Essentiellement, les êtres vivants mènent une bataille continue et difficile contre cette augmentation constante de l’entropie universelle.

Ce texte est adapté de​ <a href="https://openstax.org/books/biology-2e/pages/6-3-the-laws-of-thermodynamics">Openstax Biology 2e, Section 6.3</a><a href="https://openstax.org/books/biology-2e/pages/6-3-the-laws-of-thermodynamics"> The Laws of Thermodynamics</a>.

Entropie dans La Cellule

Les tâches principales d'une cellule vivante qui consiste à obtenir, transformer et utiliser de l'énergie pour effectuer un travail peuvent sembler simples. Cependant, la deuxième loi de la thermodynamique ...

Education

Enseignement

JoVE Core

Cell Biology

Biologie cellulaire

Unit 1

Unité 1

Energy and Catalysis

Énergie et catalyse

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

cell energy loss and entropy

Cell energy loss and entropy explain why living things need constant energy input. Cells obtain energy, transform it, and use it to do work, but these transfers are never completely efficient. In each transfer, some energy is lost in a form that cannot be used. In many cases, that lost energy is heat energy.

Cell Energy Loss and Entropy

the first law of thermodynamics

Energy Changes in Cells and Matter

The first law of thermodynamics describes how energy changes form in the universe. The total amount of energy stays constant. Energy can move from one place to another or change into a different form, but it cannot be created or destroyed. These energy changes happen in everyday life. A light bulb changes electrical energy into light energy. A gas stove changes chemical energy in natural gas into heat energy. Plants also carry out a major energy transformation when they convert sunlight energy...

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Entropy and Spontaneous Change

Entropy helps predict whether a process will happen on its own. Entropy is a measure of randomness or disorder in a system. High entropy means high disorder and low energy. A student’s bedroom is a simple example. If no work is done, the room becomes messy over time. That messy state is highly disordered and has high entropy. To make the room clean again, energy must be added as the student puts things away. That organized state has low entropy. Processes that increase the entropy of the...

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Cellular Enthalpy and Energy Changes

Cellular enthalpy describes how heat and energy change during chemical and physical processes. Enthalpy is written as H and is defined as the sum of a system’s internal energy, U, and the product of pressure and volume, PV. It is a state function, which means its value depends on the state of the system, not the path taken. Scientists cannot measure the enthalpy of a single substance directly. They can determine enthalpy changes, or ΔH, for a process instead. For reactions or changes that...

entropy within the cell

Cell energy loss and entropy explain why living things need constant energy input. Cells obtain energy, transform it, and use it to do work, but these transfers are never completely efficient. In each transfer, some energy is lost in a form that cannot be used. In many cases, that lost energy is heat energy.

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Gibbs free energy describes the usable energy in a chemical reaction. It helps scientists compare how much energy different reactions release. This measurement is called Gibbs free energy, or G, after Josiah Willard Gibbs. The second law of thermodynamics explains why not all energy stays available for work. Some energy is lost in an unusable form, such as heat, and this loss increases entropy. Gibbs free energy is the energy left after that entropy loss is taken into account. Every chemical...

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How Equilibrium Binding Constant Affects Binding

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Electron Carriers in Cell Energy Transfer

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Diffusion-Controlled Enzymes and Reaction Speed

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How Enzymes Change Shape to Catalyze

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atp energy storage and release

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ATP Powers Cellular Work

ATP powers many kinds of cellular work by coupling energy-releasing reactions to energy-requiring ones. Some reactions happen on their own and release energy. Others need an energy input to move forward. Cells link these reactions so important processes can still occur. Adenosine triphosphate, or ATP, stores energy that cells can use quickly. ATP hydrolysis is the breaking of ATP, and it releases energy. Cells often use that released energy to drive endergonic reactions, which are reactions...

key terms and concepts

Learn how cells use energy, lose some as heat, and increase entropy. See why living things must constantly take in energy to stay organized.

Cell Energy Loss and Entropy | JoVE K12

cell biology

JoVE Core Biologie cellulaire illustre les processus cellulaires complexes dans des leçons vidéos complètes mais faciles à comprendre. Cette collection se concentre sur les composants et fonctions essentiels de la cellule ; cela inclut les organelles et les membranes ainsi que le transport et le métabolisme énergétique cellulaire. Elle est complétée par nos vidéos de scientifiques à l'action qui démontrent l'application de la biologie cellulaire dans des expériences concrètes.

Texas Essential Knowledge and Skills

Biology

BIO.11

BIO.11.A

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New York State Science Learning Standards

Life Science

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Matter and Energy in Organisms and Ecosystems

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HS-PS3-6

Cell Energy Loss and Entropy

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