Name: cell reactions that release or store energy
Uploaded: 2023-04-30T10:41:14.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Chemistry

Energy

CHEM1.PS3.3

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

Endergonic and Exergonic Reactions in the Cell

如果自由能变化小于零，则该过程是自发的，称为放能反应。相反，如果自由能变化大于零，则该过程不是自发的，该反应为吸能反应。
为了比较不同反应的能量变化，通常在一组标准条件下报告自由能变化，记作 ΔG0。
在延胡索酸酶存在下，延胡索酸水合生成苹果酸的反应是一个放能反应，因为该过程的标准自由能变化为 −3.8 kJ/mol。
为了使吸能反应发生，需要向系统中加入能量。在细胞中，吸能反应会与放能反应相偶联。
例如，葡萄糖转化为葡萄糖-6-磷酸这一吸能反应的标准自由能变化为13.8 kJ/mol，而ATP的放能水解反应的标准自由能变化为&#160;−30.5 kJ/mol。
这些反应在细胞内是偶联的，整个过程为放能反应，其标准自由能变化为 −16.7 kJ/mol，即两个过程的标准自由能的总和。

细胞中的吸能和放能反应

如果化学反应过程中释放能量，则结果值将为负数。换句话说，释放能量的反应的具有ΔG < 0。负 ΔG 还意味着反应产物的自由能比反应物少，因为它们在反应过程中释放了一些自由能。科学家将具有负 ΔG 并因此释放自由能的反应称为放能反应。放能意味着能量正在离开系统。我们也将这些反应称为自发反应，因为它们可以在不向系统添加能量的情况下发生。了解哪些化学反应是自发的并释放自由能对于生物学家来说非常有用，因为可以利用这些反应在细胞内进行工作。 与日常用语中的含义相反，自发反应并不是突然或快速发生的反应。例如，铁生锈是一个缓慢发生的自发反应，随着时间的推移，慢慢地、一点一点地发生。

如果化学反应需要能量输入，则该反应的 ΔG 将是正值。在这种情况下，产物比反应物具有更多的自由能。因此，我们可以将反应产物视为能量储存分子 我们将这些化学反应称为吸能反应，它们是非自发的。如果不增加自由能，吸能反应不会自行发生。

例如，从较简单的分子构建复杂的分子（例如糖）是一个合成代谢过程，并且需要能量。因此，合成代谢过程中涉及的化学反应是吸能反应。或者，将糖分解成更简单的分子的分解代谢过程在一系列放能反应中释放能量。

如果化学反应过程中释放能量，则所得数值将为负数。换句话说，释放能量的反应具有……

Education

教育

JoVE Core

Cell Biology

细胞生物学

Unit 1

第一单元

Energy and Catalysis

能量与催化

KEY TERMS AND CONCEPTS

关键术语与概念

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 happen without adding energy to the system. In biology, this matters because cells can use these reactions to do work.

The word spontaneous does not mean fast. A spontaneous reaction can still happen slowly over time. Rusting iron is a good example. It is spontaneous, but it occurs little by little.

If a reaction needs an energy input, its ΔG is positive. In that case, the products have more free energy than the reactants. These products can be thought of as energy-storing molecules. Such reactions are called endergonic reactions, and they are non-spontaneous. They do not occur on their own unless free energy is added.

Cells use both kinds of reactions in metabolism. Building complex molecules, such as sugars, from simpler ones is an anabolic process. It requires energy, so the reactions are endergonic. Breaking sugar down into simpler molecules is a catabolic process. This breakdown releases energy in a series of exergonic reactions.

Cell Reactions That Release or Store Energy

cell-reactions-that-release-or-store-energy

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

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

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

Learn how ΔG shows whether a cell reaction is exergonic or endergonic, why spontaneous does not mean fast, and how cells use these reactions.

Cell Reactions That Release or Store Energy | 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.

Minnesota Academic Standards in Science

9-12

3.1.1 9C.2.2.1.1

Next Generation Science Standards

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-7

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

C-PS3-4

Physics

P-PS3-3

Quantifying Heat

Thermal Energy&#160;

Microscopically, thermal energy is the kinetic energy associated with the random motion of atoms and molecules. Temperature is a ...

Temperature and Thermal Equilibrium

Heat and temperature are essential concepts for everyone every day. The study of heat and temperature is part of an area of physics known as ...

Types of Kinetic Energy

The amount of kinetic energy of an object depends on its mass and speed. Consider two balls of different masses rolling down an inclined plane at the same ...

Heat Flow and Specific Heat

Heat is a type of energy transfer that is caused by a temperature difference, and it can change the temperature of an object. Since heat is a form of ...

kinetic-molecular-theory-molecular-velocities-temperature-kinetic

Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy

The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a ...

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...

Contrast the concepts of temperature and heat flow in macroscopic and microscopic terms. Understand that thermal energy is a form of energy and temperature is a measure of average kinetic energy of a particle. EXPLANATION: Students have been exposed to the types of energy (potential, kinetic, thermal, and chemical) and energy transfer (working, heating, and radiating) in the sixth grade. At that time, students classified energy types in systems and transformations. The focus in Chemistry 1 should be on understanding that measuring the temperature of a system is a way to quantify the thermal energy (average kinetic energy) of the particles in that system. Heating is a mechanism that transfers energy to or from a system. Students should also explore absolute vs relative scales of temperature mechanisms. Students should recognize that energy will always flow from objects with greater thermal energy to areas with lesser thermal energy, but rates of energy flow are a property of the materials being heated. The degree to which the temperature changes as an object is also a physical property of a material. Activities may include collecting or analyzing pressure vs temperature data, then considering why a graph of collected data does not pass through the origin. (Heat capacity and conductivity will only be assessed qualitatively.)

CHEM1.PS3.1

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Calorimetry

When objects at different temperatures are placed in contact with each other but isolated from everything else, they attain thermal equilibrium. A ...

Heat Exchanger Analysis

Source: Alexander S Rattner and Christopher J Greer; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, ...

Differential Scanning Calorimetry

Source: Danielle N. Beatty and Taylor D. Sparks, Department of Materials Science and Engineering, The University of Utah, Salt Lake City, UT
Differential ...

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant ...

Conservation of Energy

The terms &#39;conserved quantity&#39;&#160;and &#39;conservation law&#39;&#160;have specific scientific meanings in physics, which differ from the ...

Draw and interpret heating and cooling curves and phase diagrams. Analyze the energy changes involved in calorimetry by using the law of conservation of energy quantitatively (use of $q=mc\Delta T)$ and qualitatively. EXPLANATION: This is one of two standards where students are to investigate changes in a specific types of energy: In this case, thermal energy and phase energy. Starting as early as kindergarten, students are introduced to solid and liquid phases of matter. By third grade, students are considering the particulate nature of matter to discuss physical properties of the different phases. In fifth grade, students discuss phase changes from the perspective of the arrangement of particles. Chemistry 1 is the first time that students make a connection between phase changes and energy changes. Students commonly struggle with the idea that substances can be heated, but that heating does not always result in a change in temperature. Models of phase energies associated with the arrangement of particles aid in dispelling these misconceptions. Comparisons should identify similarities in energies in solids and liquids as compared to vastly different energy in gases. Discussions of heat of fusion/vaporization and calculations to enrich these discussions are appropriate. Finally, students should be able to quantify relationships in which heating creates a change in the thermal energy of a sample. Activities may include determining energy released when an object is burned to change the temperature of a substance in a closed system. (Note that this standard is limited to calculations of energy associated with changes in thermal energy, and not energies associated with phase transformations.)

CHEM1.PS3.2

Energy Transfer in Chemical Reactions

Chemical reactions require sufficient energy to cause the matter to collide with enough precision and force that old chemical bonds can be broken and new ...

energy-diagrams-transition-states-and-intermediates

Energy Diagrams, Transition States, and Intermediates

Free-energy diagrams, or reaction coordinate diagrams, are graphs showing the energy changes that occur during a chemical reaction. The reaction ...

Energy Basics

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

Chemical changes and their accompanying ...

If energy releases during a chemical reaction, then the resulting value&#160;will be a negative number. In other words, reactions that release energy have ...

Thermochemical Equations

For a chemical reaction (the system) carried out at constant pressure &ndash; with the only work done caused by expansion or contraction &ndash; the ...

Activation Energy

Activation energy is the minimum amount of energy necessary for a chemical reaction to move forward. The higher the activation energy, the slower the rate ...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

Introduction to Chemical Reactions

All chemical reactions begin with a reactant, the general term for one or more substances entering the reaction. Sodium and chloride ions, for example, ...

bond-dissociation-energy-and-activation-energy

Bond Dissociation Energy and Activation Energy

Bond energy is the energy required to break a bond homolytically. These values are usually expressed in units of kcal/mol or kJ/mol and are referred to as ...

Distinguish between endothermic and exothermic reaction by constructing potential energy diagrams and explain the differences between the two using chemical terms (e.g. activation energy). Recognize when energy is absorbed or given off depending on the bonds formed and bonds broken. EXPLANATION: This is one of two standards where students are to investigate changes in a specific type of energy: In this case, chemical energy. Students should recognize that the formation of bonds releases energy, while the breaking of bonds is endothermic. Synthesis reactions to form metal oxides can provide observations if carried out taking proper precautions. Clear changes to masses and physical properties provide evidence of a reaction. (Specific discussions of enthalpy of formation are beyond the scope of this standard, but the topic may be useful for enrichment discussions about reactions where bonds are both broken and formed.)

Conservation of Energy: Application

When solving problems using the energy conservation law, the object (system) to be studied should first be identified. Often, in applications of energy ...

conservation-of-energy-approach-to-system-analysis

Conservation of Energy Approach to System Analysis

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
The purpose of ...

What is Energy?

The universe is composed of matter in different forms, and all forms of matter contain energy. &#xA0;The different forms of energy on Earth originate from ...

First Law of Thermodynamics

Energy Conservation

Energy can be converted from one form into another, but all of the energy present before a change occurs always exists in some form ...

Conservation of Mechanical Energy

The mechanical energy E of a system is the sum of its potential energy U and the kinetic energy K of the objects within it. What happens to this ...

/files/media/science-education/science-education-thumbs/14702.jpg

Energy and Work

Source: Ketron Mitchell-Wynne, PhD,&#160;Asantha Cooray, PhD, Department of Physics &#38; Astronomy, School of Physical Sciences, University of ...

Conservative Forces

According to the law of conservation of energy, any transition between kinetic and potential energy conserves the total energy of the system. Hence, the ...

Non-conservative Forces

Non-conservative forces are dissipative forces such as friction or air resistance. These forces take energy away from a system as it progresses. Unlike ...

Energy Diagrams - I

The dynamics of a mechanical system can be easily understood by interpreting a potential energy diagram. Since energy is a scalar quantity, the ...

Energy Diagrams - II

Energy diagrams are important to understand the dynamics of a system. The topology of an energy diagram helps illustrate the equilibrium points of the ...

Analyze energy changes to explain and defend the law of conservation of energy. EXPLANATION: Standards PS3.2 and PS3.3 identify the energy types most commonly associated with chemical reactions and build on sixth grade discussions of energy storage and transfer types. In Chemistry 1, students will synthesize an understanding of law of conservation of energy by being able to distinguish system from surroundings, and recognizing that tracking energy requires both the system and surrounding energies to be considered. Students can consider interactions such as a beverage warming/cooling, a refrigerator cooling food, the function of Freon in cooling systems, or a car's cooling system as examples where multiple systems interact.

CHEM1.PS3.4

Cell Reactions That Release or Store Energy

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