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

الطاقة الداخلية ، أو E ، هي الطاقة الموجودة داخل النظام ، مثل الطاقة الموجودة في الروابط الكيميائية والحركة العشوائية لجزيئاتها. يمكن للنظام ومحيطه نقل الطاقة بينهما.
التغير في الطاقة الداخلية للنظام ، دلتا E ، يساوي مجموع q ، إجمالي الحرارة المنقولة إلى النظام ، و w ، إجمالي العمل المنجز على النظام.
في معظم التفاعلات الكيميائية الحيوية ، لا يتم تنفيذ أي عمل ؛ لذلك ، فإن التغيير في الطاقة الداخلية يعادل وظيفة ديناميكية حرارية أخرى تسمى المحتوى الحراري.
يصاحب التغيير في المحتوى الحراري للنظام أو ∆H تغيير متساو ومعاكس في المحتوى الحراري المحيط.
تحدث العملية الطاردة للحرارة عندما يطلق النظام الحرارة إلى المناطق المحيطة ويتم تمثيله بالمحتوى الحراري السلبي. تحدث عملية الماصات للحرارة عندما يكتسب النظام حرارة ، ممثلة بالمحتوى الحراري الموجب.
الخلايا الحية هي أنظمة مفتوحة تتبادل المادة والطاقة مع محيطها ، من خلال عمليات طاردة للحرارة وماصة للحرارة ، وفقا للقانون الأول للديناميكا الحرارية.

المحتوى الحراري داخل الخلية

<div style="direction: rtl;">
يستخدم المحتوى الحراري (H) لوصف الديناميكا الحرارية للعمليات الكيميائية والفيزيائية. يتم تعريف المحتوى الحراري على أنه مجموع الطاقة الداخلية للنظام (U) والمنتج الرياضي لضغطه (P) وحجمه (V):

H = U + PV

المحتوى الحراري هو أيضًا وظيفة حالة. لا يمكن قياس قيم المحتوى الحراري لمواد معينة بشكل مباشر؛ يمكن تحديد التغيرات في المحتوى الحراري للعمليات الكيميائية أو الفيزيائية فقط. بالنسبة للعمليات التي تحدث عند ضغط ثابت (حالة شائعة للعديد من التغيرات الكيميائية والفيزيائية)، فإن تغير المحتوى الحراري (ΔH) هو:

ΔH = ΔU + PΔV

الحرارة المنبعثة عند تشغيل موقد بنزن تساوي التغير في المحتوى الحراري لتفاعل احتراق الميثان الذي يحدث، لأنه يحدث عند الضغط الجوي الثابت بشكل أساسي. تشير القيمة السالبة لتغير المحتوى الحراري، ΔH < 0، إلى تفاعل طارد للحرارة؛ تشير القيمة الموجبة، ΔH > 0، إلى تفاعل ماص للحرارة.

يرتبط ΔH والتغير في الطاقة الحرة، المسمى delta G أي (∆G)، بالمعادلة التالية، والتي تُعرف باسم معادلة Gibbs Helmholtz؛

ΔG = ΔH − TΔS

نقوم عمومًا بحساب درجة الحموضة القياسية ودرجة الحرارة وظروف الضغط عند درجة حموضة 7.0 في الأنظمة البيولوجية، و25 درجة مئوية، و100 كيلوباسكال (1 بار)، على التوالي. لاحظ أن الظروف الخلوية تختلف بشكل كبير عن هذه الظروف القياسية، وبالتالي فإن قيم ∆G المحسوبة القياسية للتفاعلات البيولوجية ستكون مختلفة داخل الخلية.
</div>

يستخدم المحتوى الحراري (H) لوصف الديناميكا الحرارية للعمليات الكيميائية والفيزيائية. يعرف المحتوى الحراري بأنه مجموع الطاقة الداخلية للنظام ...

Education

JoVE Core

Cell Biology

بيولوجيا الخلية

Unit 1

الوحدة الأولى

Energy and Catalysis

الطاقة والتحفيز

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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...

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 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

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.

an introduction to free energy

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

endergonic-and-exergonic-reactions-in-the-cell

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

the-equilibrium-binding-constant-and-binding-strength

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

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

oxidation-and-reduction-of-organic-molecules

Electron Carriers in Cell Energy Transfer

Cell energy production depends on redox reactions, which are oxidation and reduction reactions that happen together. In oxidation, an electron is removed from an atom in a compound. In reduction, that same electron is added to another compound. Because these reactions usually occur as a pair, they are called redox reactions. When a molecule loses an electron, its potential energy goes down. The electron does not stay free in the cytoplasm. Instead, it moves to a second compound and reduces...

introduction to enzymes

Enzyme Function, Cofactors, and Inhibitors

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...

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...

introduction to enzyme kinetics

Graphing Enzyme Kinetics Data

Enzyme kinetics uses graphs to show how fast a biochemical reaction happens. Scientists measure the initial reaction rate, or velocity (Vo), at different substrate concentrations ([S]). They may also run trials with inhibitors or other molecules that change the reaction rate. The results are often plotted as Vo against [S]. For many single-substrate reactions, the data fits the Michaelis-Menten equation. This equation, named after Leonor Michaelis and Maud Menten, helps estimate the maximum...

turnover number and catalytic efficiency

How Fast Enzymes Work in Digestion

Enzymes can work at very different speeds, and their turnover number shows how fast they convert substrate molecules into products. Turnover number is the maximum number of substrate molecules an enzyme can transform per unit time. For most enzymes, this value is between 1 and 1000 molecules per second. Some enzymes are especially fast. Catalase has the highest known turnover number and can convert up to 2.8×10^6 molecules of hydrogen peroxide into water and oxygen each second. Lysozyme has...

catalytically perfect enzymes

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...

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

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.

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 ...

Entropy within the Cell

A living cell&#39;s primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics ...

Non-equilibrium in the Cell

An important concept in studying metabolism and energy is that of chemical equilibrium. Most chemical reactions are reversible. They can proceed in both ...

What is Photosynthesis?

Photosynthesis is a multipart, biochemical process that occurs in plants as well as in some bacteria. It captures carbon dioxide and solar energy to ...

Light as Energy

The energy required to carry out photosynthesis is light&#8212; typically electromagnetic radiation from the sun. The range of all possible wavelengths is ...

Anatomy of Chloroplasts

Green algae and plants, including green stems and unripe fruit, harbor chloroplasts&mdash;the vital organelles where photosynthesis takes place. In ...

Photosystem II

The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ...

Photosystem I

Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these ...

The Calvin Cycle

Overview

Oxygenic photosynthesis converts approximately 200 billion tons of carbon dioxide (CO2) annually to organic compounds and produces approximately ...

C4 Pathway and CAM

Most plants use the C3 pathway for carbon fixation. However, some plants, such as sugar cane, corn, and cacti that grow in hot conditions, use alternative ...

Introduction to Cellular Respiration

Organisms harvest energy from food, but this energy cannot be directly used by cells. Cells convert the energy stored in nutrients into a more usable ...

What is Glycolysis?

Overview
Cells make energy by breaking down macromolecules. Cellular respiration is the biochemical process that converts &#34;food energy&#34; (from the ...

Energy-requiring Steps of Glycolysis

Glucose is the source of nearly all energy used by organisms. The first step of converting glucose into usable energy is called glycolysis. Glycolysis ...

Energy-releasing Steps of Glycolysis

Glycolysis is divided into two phases based on whether energy is utilized or released. While the first phase consumes ATP, the second phase produces ...

Outcomes of Glycolysis

Nearly all the energy used by cells comes from the bonds that make up complex organic compounds. These organic compounds are broken down into simpler ...

Pyruvate Oxidation

After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure ...

The Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle or TCA cycle, consists of several energy-generating reactions that yield one ATP molecule, three NADH ...

Products of the Citric Acid Cycle

The cells of most organisms&#8212;including plants and animals&#8212;obtain usable energy through aerobic respiration, the oxygen-requiring version of ...

Electron Transport Chains

The final stage of cellular respiration is oxidative phosphorylation that consists of two steps: the electron transport chain and chemiosmosis. The ...

Chemiosmosis

Oxidative phosphorylation is a highly efficient process that generates large amounts of adenosine triphosphate (ATP), the basic unit of energy that drives ...

Electron Carriers

Electron carriers can be thought of as electron shuttles. These compounds can easily accept electrons (i.e., be reduced) or lose them (i.e., be oxidized). ...

ATP Yield

Cellular respiration produces 30 - 32 ATP per glucose molecule. Although most of the ATP results from oxidative phosphorylation and the electron transport ...

Fermentation

Most eukaryotic organisms require oxygen to survive and function adequately. Such organisms produce large amounts of energy during aerobic respiration by ...

Dietary Connections

In biological systems, most metabolic pathways are interconnected. The cellular respiration processes that convert glucose to ATP&#8212;such as ...

Explain how matter is conserved and energy is transferred during photosynthesis and cellular respiration using models, including the chemical equations for these processes.

Introduction to Enzymes

The use of enzymes by humans dates to 7000 BCE. Humans first used enzymes to ferment sugars and produce alcohol without knowing that this was an ...

Enzymes and Activation Energy

The activation energy (or free energy of activation), abbreviated as Ea, is the small amount of energy input necessary for all chemical reactions to ...

Introduction to Enzyme Kinetics

Enzyme kinetics studies the rates of biochemical reactions. Scientists monitor the reaction rates for a particular enzymatic reaction at various substrate ...

Introduction to Mechanisms of Enzyme Catalysis

For many years, scientists thought that enzyme-substrate binding took place in a simple &#34;lock-and-key&#34; fashion. This model stated that the enzyme ...

Ligand Binding and Linkage

Cooperative Allosteric Transitions

Ribozymes

ATP Energy Storage and Release

ATP is a highly unstable molecule. Unless quickly used to perform work, ATP spontaneously dissociates into ADP and inorganic phosphate (Pi), and the free ...

ATP and Macromolecule Synthesis

Biological macromolecules are organic compounds, predominantly composed of carbon atoms. The carbon atoms are covalently bonded with hydrogen, oxygen, ...

Coupled Reactions

Cellular processes such as building and breaking down complex molecules occur through stepwise chemical reactions. Some of these chemical reactions are ...

Overview of Metabolism

Living cells constantly carry out various chemical reactions which are necessary for their proper functioning. These reactions are interlinked to one ...

Overview of Carbohydrate Metabolism

During digestion, polysaccharides are broken down into simple sugars.
After their absorption in the GI tract, glucose is transported into other cells ...

Overview of Protein Metabolism

During digestion, proteins are broken down into smaller peptides and amino acids, which are absorbed.
The amino acids are not stored for later use. ...

Overview of Lipid Metabolism

Lipid metabolism includes lipolysis and lipogenesis.
In lipolysis, dietary triglycerides are converted into fatty acids and glycerol, producing ATPs ...

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

Description

Transcript

More videos by Standards