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

The internal energy, or E, is the energy contained within a system, such as the energy contained in chemical bonds and the random motion of its particles. A system and its surroundings can transfer energy between them.
The change in internal energy of a system, delta E, is equal to the sum of q, the total heat transferred to the system, and w, the total work done on the system.
In most biochemical reactions, no work is performed; therefore, the change in internal energy is equivalent to another thermodynamic function called enthalpy.
The change in enthalpy of a system or &#8710;H is accompanied by an equal and opposite change in the enthalpy of the surroundings.
An exothermic process is when the system releases heat to the surroundings and is represented by a negative enthalpy. An endothermic process is when the system gains heat, represented by a positive enthalpy.
Living cells are open systems that exchange matter and energy with their surroundings, through exothermic and endothermic processes, following the first law of thermodynamics.

enthalpie binnen de cel

Enthalpie (H) wordt gebruikt om de thermodynamica van chemische en fysische processen te beschrijven. Enthalpie wordt gedefinieerd als de som van de interne energie van een systeem (U) en het wiskundige product van de druk (P) en het volume (V):

H = U + PV

Enthalpie is ook een toestandsfunctie. Enthalpiewaarden voor specifieke stoffen kunnen niet direct worden gemeten; alleen enthalpieveranderingen voor chemische of fysische processen kunnen worden bepaald. Voor processen die plaatsvinden bij constante druk (een veel voorkomende voorwaarde voor veel chemische en fysische veranderingen), is de enthalpieverandering (ΔH):

ΔH = ΔU + PΔV

De warmte die vrijkomt wanneer u een bunsenbrander gebruikt, is gelijk aan de enthalpieverandering van de methaanverbrandingsreactie die plaatsvindt, aangezien deze plaatsvindt bij de in wezen constante druk van de atmosfeer. Een negatieve waarde van een enthalpieverandering, ΔH <0, duidt op een exotherme reactie; een positieve waarde, ΔH > 0, duidt op een endotherme reactie.

De ΔH en de verandering in vrije energie, delta G (∆G) genoemd, houden verband met de volgende vergelijking, die bekend staat als de Gibbs Helmholtz-vergelijking;

ΔG = ΔH − TΔS

Over het algemeen berekenen we standaard pH-, temperatuur- en drukomstandigheden bij pH 7,0 in biologische systemen, respectievelijk 25 graden Celsius en 100 kilopascal (1 bar). Merk op dat de cellulaire omstandigheden aanzienlijk verschillen van deze standaardomstandigheden, en dat de standaard berekende ∆G-waarden voor biologische reacties dus binnen de cel anders zullen zijn.

Enthalpie binnen de cel

Enthalpy (H) is used to describe the thermodynamics of chemical and physical processes. Enthalpy is defined as the sum of a system&#39;s internal energy ...

Education

JoVE Core

Cell Biology

Celbiologie

Unit 1

Eenheid 1

Energy and Catalysis

Energie en Katalyse

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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

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 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 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

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an introduction to free energy

Gibbs Free Energy and Reaction Work

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endergonic and exergonic reactions in the cell

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Cell Reactions That Release or Store Energy

Cell reactions can either release energy or store it for later use. In chemistry, this difference is described by the value of ΔG, or free energy change. When energy is released during a reaction, ΔG is negative. The products then have less free energy than the reactants because some free energy has been given off. Reactions with a negative ΔG are called exergonic reactions. Exergonic means energy is leaving the system. These reactions are also called spontaneous reactions because they can...

the equilibrium binding constant and binding strength

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How Equilibrium Binding Constant Affects Binding

The equilibrium binding constant describes how strongly two molecules bind at equilibrium. It is a useful way to compare binding strength in molecular interactions. This topic focuses on how binding is measured and what the equilibrium binding constant means. A higher value indicates stronger binding, while a lower value indicates weaker binding. Understanding this constant helps explain how tightly molecules stay together under equilibrium conditions. The page also connects the binding...

free energy and equilibrium

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

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oxidation and reduction of organic molecules

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enzymes and activation energy

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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turnover number and catalytic efficiency

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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.

introduction to mechanisms of enzyme catalysis

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

Ligand binding and linkage describe how one molecule can affect another when it binds to a protein. In this topic, the focus is on how binding at one site can influence activity at a different site on the same protein. This idea is important for understanding protein function in high school biology. It helps explain why some proteins respond more strongly after a ligand attaches. The transcript centers on the connection between ligand binding and linkage, which is a key concept in molecular...

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ribozymes

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atp energy storage and release

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key terms and concepts

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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Chemiosmosis

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Ligand Binding and Linkage

Cooperative Allosteric Transitions

Ribozymes

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Investigate and explain the role of enzymes in facilitating cellular processes.

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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