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

Die innere Energie oder E ist die Energie, die in einem System enthalten ist, wie z. B. die Energie, die in chemischen Bindungen und der zufälligen Bewegung seiner Teilchen enthalten ist. Ein System und seine Umgebung können Energie zwischen ihnen übertragen.
Die Änderung der internen Energie eines Systems, Delta E, ist gleich der Summe aus q, der gesamten Wärme, die an das System übertragen wird, und w, der gesamten Arbeit, die am System geleistet wird.
Bei den meisten biochemischen Reaktionen wird keine Arbeit geleistet; daher ist die Änderung der inneren Energie äquivalent zu einer anderen thermodynamischen Funktion, die Enthalpie genannt wird.
Die Änderung der Enthalpie eines Systems oder ∆H geht einher mit einer gleichen und entgegengesetzten Änderung der Enthalpie der Umgebung.
Ein exothermer Prozess liegt vor, wenn das System Wärme an die Umgebung abgibt und durch eine negative Enthalpie dargestellt wird. Ein endothermer Prozess liegt vor, wenn das System Wärme gewinnt, die durch eine positive Enthalpie dargestellt wird.
Lebende Zellen sind offene Systeme, die Materie und Energie mit ihrer Umgebung austauschen, und zwar durch exotherme und endotherme Prozesse, die dem ersten Hauptsatz der Thermodynamik folgen.

enthalpie innerhalb der zelle

Enthalpie (H) wird zur Beschreibung der Thermodynamik chemischer und physikalischer Prozesse verwendet. Enthalpie ist definiert als die Summe der inneren Energie (U) eines Systems und dem mathematischen Produkt aus Druck (P) und Volumen (V):

H = U + PV

Auch die Enthalpie ist eine Zustandsfunktion. Enthalpiewerte für bestimmte Substanzenkönnen nicht direkt gemessen werden; Es können nur Enthalpieänderungen für chemische oder physikalische Prozesse bestimmt werden. Für Prozesse, die bei konstantem Druck ablaufen (eine häufige Bedingung für viele chemische und physikalische Veränderungen), beträgt die Enthalpieänderung (ΔH):

ΔH = ΔU + PΔV

Die beim Betrieb eines Bunsenbrenners abgegebene Wärme entspricht der Enthalpieänderung der stattfindenden Methanverbrennungsreaktion, da diese bei im Wesentlichen konstantem Druck der Atmosphäre stattfindet. Ein negativer Wert einer Enthalpieänderung, ΔH < 0, weist auf eine exotherme Reaktion hin; Ein positiver Wert, ΔH > 0, weist auf eine endotherme Reaktion hin.

ΔH und die Änderung der freien Energie, Delta G (∆G) genannt, hängen durch die folgende Gleichung zusammen, die als Gibbs-Helmholtz-Gleichung bekannt ist;

ΔG = ΔH − TΔS

Wir berechnen im Allgemeinen Standard-pH-, Temperatur- und Druckbedingungen bei pH 7,0 in biologischen Systemen, 25 Grad Celsius bzw. 100 Kilopascal (1 bar). Beachten Sie, dass die zellulären Bedingungen erheblich von diesen Standardbedingungen abweichen und daher die standardmäßig berechneten ∆G-Werte für biologische Reaktionen innerhalb der Zelle unterschiedlich sein werden.

Dieser Text ist adaptiert von Openstax, Biology 2e, <a href="https://openstax.org/books/biology-2e/pages/6-3-the-laws-of-thermodynamics">Section 6.3: The Laws of Thermodynamics</a> und Openstax, Chemie 2e ,<a href="https://openstax.org/books/chemistry-2e/pages/5-3-enthalpy">Section 5.3: Enthalpy.</a>

Enthalpie innerhalb der Zelle

Die Enthalpie (H) wird verwendet, um die Thermodynamik chemischer und physikalischer Prozesse zu beschreiben. Die Enthalpie ist definiert als die Summe der inneren Energie eines Systems ...

Education

Lehre

JoVE Core

Cell Biology

Zellbiologie

Unit 1

Einheit 1

Energy and Catalysis

Energie und Katalyse

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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

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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

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JoVE Core Zellbiologie veranschaulicht komplexe zelluläre Prozesse in leicht verständlichen und dennoch umfassenden animierten Videolektionen. Diese Sammlung konzentriert sich auf die wesentlichen Bestandteile und Funktionen von Zellen, einschließlich Organellen und Membranen, Zelltransport und Zellenergie. Ergänzt wird sie durch Videos von Wissenschaftlern in Aktion, die die Anwendung der Zellbiologie in realen Forschungsexperimenten demonstrieren.

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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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