Name: cellular enthalpy and energy changes
Uploaded: 2023-04-30T10:40:59.000Z
Duration: 1 min 18 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Biology

BIO.11

BIO.11.A

Enthalpy within the Cell

L'energia interna, o E, è l'energia contenuta all'interno di un sistema, come l'energia contenuta nei legami chimici e il movimento casuale delle sue particelle. Un sistema e l'ambiente circostante possono trasferire energia tra di loro.
La variazione dell'energia interna di un sistema, delta E, è uguale alla somma di q, il calore totale trasferito al sistema, e w, il lavoro totale svolto sul sistema.
Nella maggior parte delle reazioni biochimiche, non viene eseguito alcun lavoro; quindi, la variazione dell'energia interna è equivalente a un'altra funzione termodinamica chiamata entalpia.
La variazione di entalpia di un sistema o ∆H è accompagnata da una variazione uguale e contraria dell'entalpia dell'ambiente circostante.
Un processo esotermico è quando il sistema rilascia calore nell'ambiente circostante ed è rappresentato da un'entalpia negativa. Un processo endotermico è quando il sistema guadagna calore, rappresentato da un'entalpia positiva.
Le cellule viventi sono sistemi aperti che scambiano materia ed energia con l'ambiente circostante, attraverso processi esotermici ed endotermici, seguendo il primo principio della termodinamica.

entalpia all'interno della cellula

L'entalpia (H) viene utilizzata per descrivere la termodinamica dei processi chimici e fisici. L'entalpia è definita come la somma dell'energia interna di un sistema (U) e il prodotto matematico della sua pressione (P) e del volume (V):

H = U + PV

Anche l’entalpia è una funzione di stato. I valori di entalpia per sostanze specifiche non possono essere misurati direttamente; è possibile determinare solo le variazioni di entalpia per processi chimici o fisici. Per i processi che avvengono a pressione costante (una condizione comune per molti cambiamenti chimici e fisici), la variazione di entalpia (ΔH) è:

ΔH = ΔU + PΔV

Il calore emesso quando si utilizza un becco di Bunsen è uguale alla variazione di entalpia della reazione di combustione del metano che avviene, poiché avviene alla pressione sostanzialmente costante dell'atmosfera. Un valore negativo di una variazione di entalpia, ΔH < 0, indica una reazione esotermica; un valore positivo, ΔH > 0, indica una reazione endotermica.

Il ΔH e la variazione di energia libera, chiamata delta G (∆G), sono correlati dalla seguente equazione, nota come equazione di Gibbs Helmholtz:

ΔG = ΔH − TΔS

Generalmente calcoliamo le condizioni standard di pH, temperatura e pressione a pH 7,0 nei sistemi biologici, 25 gradi Celsius e 100 kilopascal (1 bar). Si noti che le condizioni cellulari variano considerevolmente da queste condizioni standard, quindi i valori ∆G calcolati standard per le reazioni biologiche saranno diversi all'interno della cellula.

Questo testo è adattato da Openstax, Biologia 2e,<a href="https://openstax.org/books/biology-2e/pages/6-3-the-laws-of-thermodynamics">Section 6.3: The Laws of Thermodynamics</a> e Openstax, Chimica 2e, <a href="https://openstax.org/books/chemistry-2e/pages/5-3-enthalpy">Section 5.3: Enthalpy.</a>

Entalpia all'interno della cellula

L'entalpia (H) è usata per descrivere la termodinamica dei processi chimici e fisici. L'entalpia è definita come la somma dell'energia interna di un sistema ...

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

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 occur at constant pressure, which is common in many chemical and physical processes, ΔH equals ΔU + PΔV.

A simple example is the heat released when a Bunsen burner burns methane. That heat is equal to the enthalpy change of the combustion reaction because the reaction happens at essentially constant atmospheric pressure. A negative ΔH means the reaction is exothermic, while a positive ΔH means it is endothermic.

Enthalpy also connects to free energy through the Gibbs-Helmholtz equation, ΔG = ΔH − TΔS. In biology, standard conditions are usually pH 7.0, 25 degrees Celsius, and 100 kilopascals, or 1 bar. Cellular conditions often differ from these standards, so standard calculated ΔG values for biological reactions can change inside the cell.

Cellular Enthalpy and Energy Changes

the first law of thermodynamics

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enthalpy within the cell

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...

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the equilibrium binding constant and binding strength

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oxidation and reduction of organic molecules

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introduction to mechanisms of enzyme catalysis

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Explore enthalpy, ΔH, and Gibbs free energy in cells. Learn how constant pressure, exothermic and endothermic reactions, and cellular conditions affect energy change.

Cellular Enthalpy and Energy Changes | 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.

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BIO.11.B

Science concepts--biological structures, functions, and processes. The student knows the significance of matter cycling, energy flow, and enzymes in living organisms. The student is expected to:

Cellular Enthalpy and Energy Changes

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