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

Le cellule viventi seguono la seconda legge della termodinamica, che afferma che i sistemi tendono a procedere da stati ordinati a bassa entropia a stati disordinati ad alta entropia senza input esterni.
Ad esempio, il trasporto passivo di ossigeno concentrato dai polmoni al sangue meno ossigenato disperde le molecole di ossigeno, aumentando l'entropia del sistema.
Le cellule traggono energia dalla scomposizione di molecole come il glucosio. I sottoprodotti della reazione – anidride carbonica, acqua e calore vengono rilasciati nell'ambiente circostante, aumentandone l'entropia.
La sopravvivenza cellulare dipende da sistemi altamente ordinati come il DNA e le proteine. La formazione di queste strutture ordinate provoca una diminuzione dell'entropia del sistema, che deve essere accompagnata da un aumento uguale o maggiore dell'entropia dell'ambiente circostante.
I singoli filamenti di DNA sono disordinati e la loro entropia diminuisce quando si riuniscono in una struttura a doppia elica ordinata.
Allo stesso tempo, l'energia viene rilasciata nell'ambiente circostante durante la formazione della doppia elica. Questa energia rende l'ambiente circostante più disordinato e ne aumenta l'entropia.

entropia all'interno della cellula

I compiti primari di una cellula vivente, ovvero ottenere, trasformare e utilizzare l'energia per svolgere un lavoro, possono sembrare semplici. Tuttavia, la seconda legge della termodinamica spiega perché questi compiti sono più difficili di quanto sembri. Nessuno dei trasferimenti di energia nell’universo è completamente efficiente. In ogni trasferimento di energia, una parte di energia viene persa in una forma inutilizzabile. Nella maggior parte dei casi, questa forma è energia termica. Dal punto di vista termodinamico, l’energia termica è definita come l’energia trasferita da un sistema all’altro che non rappresenta lavoro. Ad esempio, una parte dell'energia viene persa sotto forma di energia termica durante le reazioni metaboliche cellulari.

Un concetto importante nei sistemi fisici è quello di ordine e disordine. Maggiore è l’energia dispersa da un sistema nell’ambiente circostante, meno ordinato e più casuale sarà il sistema. Gli scienziati chiamano entropia la misura della casualità o del disordine all’interno di un sistema. Alta entropia significa alto disordine e bassa energia. Anche le molecole e le reazioni chimiche hanno un'entropia variabile. Ad esempio, l’entropia aumenta quando le molecole ad alta concentrazione in un punto si diffondono e si diffondono.

Gli esseri viventi sono altamente ordinati e richiedono un costante apporto di energia per essere mantenuti in uno stato di bassa entropia. Quando i sistemi viventi assorbono molecole che immagazzinano energia e le trasformano attraverso reazioni chimiche, perdono una certa quantità di energia utilizzabile nel processo perché nessuna reazione è completamente efficiente. Producono anche rifiuti e sottoprodotti che non costituiscono fonti energetiche utili. Questo processo aumenta l'entropia dell'ambiente circostante il sistema. Poiché tutti i trasferimenti di energia comportano la perdita di una parte di energia utilizzabile, la seconda legge della termodinamica afferma che ogni trasferimento o trasformazione di energia aumenta l’entropia dell’universo. Anche se gli esseri viventi sono altamente ordinati e mantengono uno stato di bassa entropia, l’entropia totale dell’universo è in costante aumento a causa della perdita di energia utilizzabile ad ogni trasferimento di energia che avviene. In sostanza, gli esseri viventi sono in una continua battaglia contro questo costante aumento dell’entropia universale.

Questo testo è adattato da <a href="https://openstax.org/books/biology-2e/pages/6-3-the-laws-of-thermodynamics">Openstax Biology 2e, Section 6.3 The Laws of Thermodynamics.</a>

Entropia all'interno della cellula

I compiti primari di una cellula vivente di ottenere, trasformare e utilizzare l'energia per svolgere il lavoro possono sembrare semplici. Tuttavia, la seconda legge della termodinamica ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Energy and Catalysis

Energia e Catalisi

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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...

the second law of thermodynamics

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...

enthalpy within the cell

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 and Reaction Work

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...

endergonic and exergonic reactions in the cell

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Cell Reactions That Release or Store Energy

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the equilibrium binding constant and binding strength

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How Equilibrium Binding Constant Affects Binding

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Free Energy and Reaction Direction

Free energy and reaction direction are linked in chemical equilibrium. A free energy change, ΔG, shows the driving force for a process. When ΔG is negative, the process is driven forward. When ΔG is positive, the reverse direction is favored. When ΔG is zero, the forward and reverse driving forces are equal, and the system is at equilibrium. The reaction quotient, Q, helps show how close a system is to equilibrium. Q is the numerical value of the mass action expression for the system. It can...

non-equilibrium in the cell

Cells Stay Out of Equilibrium

Cells stay out of chemical equilibrium by constantly using energy and moving materials in and out. Chemical reactions in metabolism are often reversible. They can go in both directions. In one direction, they release energy to the surroundings. In the reverse direction, they absorb energy. The same idea applies to reactions that build and break down cell molecules. Proteins, for example, can be broken into individual amino acids, and amino acids can be used to build proteins again. In a closed...

oxidation and reduction of organic molecules

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Electron Carriers in Cell Energy Transfer

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Enzymes are proteins that speed up biochemical reactions without being used up. Humans have used enzymes since about 7000 BCE, when they fermented sugars to make alcohol without knowing the reaction was enzyme-catalyzed. The word enzyme was coined by Wilhelm Kuhne in 1877. It comes from the Greek words en, meaning “in” or “within,” and zyme, meaning “yeast.” Enzymes work through active sites, which are regions that bind substrates and help convert them into products. Many enzymes also have...

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How Enzymes Lower Reaction Energy

Enzymes lower the energy needed for a chemical reaction to begin. That starting energy is called activation energy, or free energy of activation, and it is often written as Ea. During a reaction, bonds break and new bonds form. In glucose breakdown, for example, bonds between carbon atoms break and release energy because they are energy-storing bonds. Before a reaction can move forward, reactant molecules must reach a high-energy, unstable shape called the transition state. To get there, the...

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Graphing Enzyme Kinetics Data

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How Fast Enzymes Work in Digestion

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Diffusion-Controlled Enzymes and Reaction Speed

Catalytically perfect enzymes are enzymes that speed up biochemical reactions at very high rates. The idea was first proposed by W. J. Albery and J. R. Knowles in 1976. These enzymes have catalytic efficiency values of about 10^8 to 10^9 M^-1 s^-1 and are also called diffusion-controlled enzymes because diffusion of the substrate into the active site is the only rate-limiting step. Examples of catalytically perfect enzymes include triose phosphate isomerase, fumarase, and superoxide dismutase.

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introduction-to-mechanisms-of-enzyme-catalysis

How Enzymes Change Shape to Catalyze

Enzyme catalysis depends on how enzymes bind substrates and how the active site responds during the reaction. Scientists once described this process with a simple lock-and-key model, where the enzyme and substrate fit together in one instant. Research now supports induced fit, a more dynamic model in which binding causes a small change in the enzyme’s shape. That shift helps create an ideal match between the enzyme and the substrate’s transition state, which improves catalysis. The active site...

ligand binding and linkage

Ligand Binding and Allosteric Effects

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cooperative allosteric transitions

How Proteins Shift Shape Together

Proteins can change shape in a coordinated way during allosteric transitions. In a cooperative transition, one part of the protein affects another part, so the change spreads through the molecule. These shape changes help proteins switch between different states. The shift can influence how the protein works and how it responds to other molecules. Cooperative allosteric transitions are an important idea in protein function. They explain how a small change at one site can lead to a larger...

ribozymes

Catalytic RNA: Ribozymes in Action

Ribozymes are RNA molecules that can act as enzymes. They help speed up specific chemical reactions without being protein enzymes. This makes them an important example of RNA with more than one job in the cell. Some ribozymes can cut RNA molecules, and others can join them together. This shows that RNA can do catalytic work as well as carry genetic information. Ribozymes are a key part of how scientists think about the many roles of RNA in biology. One well-known ribozyme is ribonuclease P,...

atp energy storage and release

ATP Powers Cellular Transport and Reactions

ATP powers cellular transport and many reactions by transferring energy through phosphorylation. ATP is a highly unstable molecule. If it is not used quickly, it breaks down into ADP and inorganic phosphate, and the released energy is lost as heat. Cells use ATP through energy coupling. This means the exergonic reaction of ATP hydrolysis is linked to an endergonic reaction so the reaction can move forward. One major example is the sodium-potassium pump, a transmembrane ion pump that is vital...

atp and macromolecule synthesis

ATP in Building Cell Macromolecules

ATP helps cells build biological macromolecules. These organic compounds are mainly made of carbon atoms bonded to hydrogen, oxygen, nitrogen, and small amounts of other elements. The four major classes of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Most macromolecules start as small subunits called monomers. Cells join monomers with covalent bonds to make larger molecules called polymers. This building process needs energy, so cells depend on ATP, the...

coupled reactions

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 Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Texas Essential Knowledge and Skills

Biology

BIO.11

BIO.11.A

new-york-state-science-learning-standards

New York State Science Learning Standards

Life Science

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Matter and Energy in Organisms and Ecosystems

HS-LS2-4.

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HS-PS3-3

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Entropy

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HS-PS3-4

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HS-PS3-6

Cell Energy Loss and Entropy

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