Name: enzyme action and inhibition
Uploaded: 2020-09-24T15:06:50.000Z
Duration: 2 min 34 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.5.1

Enzymes

Ферменты это биологические катализаторы, ускоряющие биохимические реакции. Большинство ферментов это белки, состоящие из аминокислот;некоторые из них представляют собой молекулы РНК, известные как рибозимы. Ферменты действуют за счет снижения энергии активации реакции, тем самым увеличивая скорость реакции.Они могут катализировать как синтез, так и разрушение химических связей, но не влияют на направление или равновесие реакции. Каждый фермент связывается с определенным исходным веществом, называемым субстратом, и катализирует определенную реакцию. Субстрат связывается с отдельной каталитической областью фермента, называемой активным центром, посредством взаимодействий, таких как межмолекулярные силы и временные ковалентные связи, в результате чего образуется комплекс фермент-субстрат.Это связывание является высокоспецифичным из-за необходимой конформационной комплементарности между ферментом и его субстратом. Таким образом, конкретный фермент может катализировать определенные реакции только в зависимости от его конформации. Простым способом понимания образования комплексов является модель замок-ключ"которая предполагает, что субстрат входит в активный сайт фермента, аналогично ключу"вставляемому в соответствующий замок"Однако другая модель, модель индуцированной подгонки, учитывает динамическую природу комплекса.Эта модель утверждает, что, когда субстрат связывается с ферментом, он вызывает небольшие конформационные изменения, приводящие к более плотному прилеганию, которое способствует реакции. Энергию активации реакции можно снизить различными способами. Общие механизмы включают индуцирование конформационных изменений в субстрате, которые позволяют легче разорвать связь, или сближение реакционных групп двух субстратов, тем самым способствуя образованию связи.Активность ферментов может быть временно или постоянно подавлена природными или синтетическими молекулами, называемыми ингибиторами. Например, конкурентный ингибитор конкурирует с субстратом за связывание с активным участком фермента, тем самым предотвращая связывание субстрата. С другой стороны, неконкурентный ингибитор связывается с другим участком фермента, что вызывает конформационные изменения в активном участке, снижая каталитическую активность sфермента.

Ферменты

Внутри живых организмов ферменты выступают в качестве катализаторов многих биохимических реакций, связанных с клеточным метаболизмом. Роль энзимов заключается в уменьшении энергий активации биохимических реакций путем формирования комплексов с его субстратами. Снижение энергий активации благоприятно для повышения темпов биохимических реакций. 
 Дефицит фермента часто может привести к опасным для жизни заболеваниям. Например, генетическая аномалия, приводющая к дефициту фермента G6PD (глюкоза-6-фосфатдегидрогеназа), отрицательно влияет на метаболический путь, по которого NADPH поставляет клеткам. 
 Нарушение этого метаболического пути может привести к уменьшению глутатиона в эритроцитах, что может привести к повреждению других энзимов и белков, таких как гемоглобин. Избыточная метаболизация гемоглобина повышает уровень билирубина, что приводит к желтухе, что может стать серьезным. Таким образом, люди, страдающие от дефицита G6PD, должны избегать некоторых продуктов питания и лекарств, содержащих химические вещества, которые могут вызвать повреждение их глутатионно-дефицитных эритроцитов. 
 Функция и структура фермента 
 Ферменты группируются по разным классам в зависимости от конкретной функции, которую они выполняют. Например, окислоредуктазы участвуют в окислительно-восстановительных реакциях, в то время как трансферазы катализируют перенос функциональных групп. Формирование связей с гидролизом АТФ требует лигаз, в то время как реакции гидролиза и образование двойных связей катализируются гидролазами и лиазами соответственно. Ферменты Isomerase обычно катализируют реакции изомеризации. 
 Ферменты обычно обладают активными участками. Это специфические области на молекуле с конформацией, которая предпочитает фермент связывать с конкретным субстратом (молекулой реагент), образуя комплекс фермента-субстрата или реактивный промежуточный. 
 Две модели — модель с блокировкой и ключом и модель с индуцированной посадкой — пытаются объяснить работу активной площадки (рис. 1). Самая упрощенная гипотеза о блокировке и ключе позволяет сделать вывод, что активная область и молекулярная форма подложки являются взаимодополняющими, объединяя их, как ключ в замке (рис. 1a). С другой стороны, гипотеза индуцированной пригонки предполагает, что молекула фермента является гибкой и изменяет форму для размещения связи с субстратом (рисунок 1b). 
 Однако и модель блокировки-ключа, и модель индуцированной подгонки учитывают тот факт, что ферменты могут связываться только с определенными субстратами и катализировать только определенную реакцию. 
 <img alt=""Eq1"" src=""/files/ftp_upload/11384/11384_Image_1.png"" style=""text-align: center; height: 300px;"" />
 Рисунок 1 (a) в зависимости от модели с замком, форма активного участка фермента идеально подходит для субстрата. (b) в зависимости от модели наведенной посадки активный участок является несколько гибким и может изменить форму для связи с подложкой. 
 Ингибиторы фермента 
 Активность фермента также может быть прервана процессом ингибирования фермента. Существует несколько распространенных типов ингибитирования фермента. 
 Во время конкурентного торможения молекула (натуральная или синтетическая), кроме субстрата, напрямую связывается с активным участком фермента. Структурное и химическое сходство ингибитора с субстратом облегчает его привязку к активному участку. Такие ингибиторы конкуренции, таким образом, конкурируют с субстратами, предотвращая их связывание с фермента. Чаще всего увеличение концентрации субстрата может подавить эффекты конкурентного торможения. 
 При неконкурентном угнетении молекула (натуральная или синтетическая) связывается с аллостерической (другой) областью фермента, отличной от его активного участка. Связывание ингибитора вызывает конформное изменение активной области фермента, в результате чего снижается способность фермента катализировать реакцию. В отличие от конкурентного торможения, увеличение концентрации субстрата не смягчает тормозящего эффекта неконкурентного торможения. 
 Часть этого текста адаптирована из<a href=""https://openstax.org/books/chemistry-2e/pages/12-7-catalysis""> Openstax, Химия 2е изд., раздел 12.7: Катализ. </a>

Внутри живых организмов ферменты действуют как катализаторы многих биохимических реакций, участвующих в клеточном метаболизме. Роль ферментов заключается в снижении ...

Education

JoVE Core

Химия

Один

Chemical Kinetics

Химическая кинетика

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

enzyme action and inhibition

Enzymes are biological catalysts that speed up many reactions in living organisms. They help control cellular metabolism by lowering the activation energy needed for biochemical reactions. When activation energy drops, reaction rates can increase.

Enzyme problems can also lead to serious disease. A genetic abnormality that causes G6PD, or glucose-6-phosphate dehydrogenase, deficiency can disrupt the pathway that supplies NADPH to cells. In red blood cells, this can reduce glutathione and damage other enzymes and proteins such as hemoglobin. As hemoglobin is broken down too much, bilirubin builds up and can cause jaundice. People with G6PD deficiency often need to avoid certain foods and medicines that may trigger damage to their red blood cells.

Enzymes are grouped by the reactions they carry out. Oxidoreductases take part in redox reactions. Transferases move functional groups from one molecule to another. Ligases form bonds and use ATP hydrolysis, while hydrolases drive hydrolysis reactions and lyases help form double bonds. Isomerases catalyze isomerization reactions.

Most enzymes have an active site, which is the region that binds a specific substrate, or reactant molecule. The enzyme and substrate form an enzyme-substrate complex, which acts as the reaction intermediate. Two models explain how this binding works. In the lock-and-key model, the active site and substrate fit together like a key in a lock. In the induced-fit model, the enzyme changes shape to fit the substrate. Both models explain enzyme specificity, meaning an enzyme usually binds only certain substrates and catalyzes only one particular reaction.

Enzyme activity can also be blocked by inhibitors. In competitive inhibition, an inhibitor that is similar to the substrate binds directly to the active site and competes with the substrate. Increasing substrate concentration can often reduce this effect. In non-competitive inhibition, the inhibitor binds to an allosteric site, which is a different region of the enzyme. This binding changes the shape of the active site and lowers enzyme activity. Unlike competitive inhibition, adding more substrate does not fix non-competitive inhibition.

Enzyme Action and Inhibition

reaction rate

Measuring Reaction Rates

Measuring reaction rates shows how fast reactants are used up or products are formed over time. The rate of reaction is the change in the amount of a reactant or product per unit time. Because of that, scientists measure how a property changes as the reaction proceeds and connect that change to reactant or product amounts. For reactions that make or use a gas, the rate can be followed by changes in volume or pressure. A rate expression is the mathematical way to write how concentration changes...

measuring reaction rates

Tracking Reaction Kinetics with Light and Pressure

Reaction kinetics can be tracked with polarimetry, spectrometry, and pressure measurements. These methods let scientists follow a reaction without disturbing the sample. They also help determine how reactant or product concentrations change over time. Polarimetry is used for optically active substances. These substances rotate the plane of polarized light, which is called optical rotation. The effect comes from molecular structure. Normal monochromatic light is unpolarized, but after it passes...

concentration and rate law

Reaction Order from Concentration

Reaction order from concentration shows how reactant amounts affect reaction rate. Rate laws, also called differential rate laws or rate equations, are mathematical expressions that connect reaction rate with the concentrations of reactants. For a generic reaction a A + b B → products, the rate law can be written using the reactant concentrations [A] and [B] and a rate constant k. In a rate law, k is the rate constant for one specific reaction at one specific temperature. The exponents m and n...

determining order of reaction

Finding Rate Law from Initial Rates

Rate laws connect the speed of a chemical reaction to the concentration of its reactants. The rate constant, k, and the reaction orders are not taken from the chemical equation. They are found experimentally by watching how the rate changes when the reactant concentrations change. One common way to do this is the method of initial rates. In this method, several trials are run with different starting concentrations. The measured rates are then compared to determine the reaction orders and,...

the integrated rate law: the dependence of concentration on time

the-integrated-rate-law-the-dependence-of-concentration-on-time

Reading Reaction Progress with Integrated Laws

Integrated rate laws connect reaction concentration to time. They help show how much reactant or product is present after a certain period. They can also help estimate how long a reaction must run to reach a given extent. A common use is finding how long radioactive material must be stored before its radioactivity drops to a safe level. These equations come from the differential rate law after it is integrated with respect to time. For a first-order reaction, where rate = k[A], the integrated...

half-life of a reaction

Reaction Half-Life in Kinetics

Reaction half-life is the time needed for half of a reactant to be consumed. After each half-life, half of the remaining reactant is used up. A hydrogen peroxide decomposition example shows this pattern clearly. The concentration drops from 1.000 M to 0.500 M in the first 6.00 hours, then to 0.250 M in the next 6.00 hours, and then to 0.125 M in the third period. Each later 6.00-hour interval removes half of what is left. For first-order reactions, the half-life does not depend on the reactant...

temperature dependence on reaction rate

Collision Theory and Reaction Speed

Collision theory explains why reaction speed depends on how particles collide. Atoms, molecules, or ions must come close together before they can react. The theory says the reaction rate depends on the collision rate, the orientation of the colliding species, and whether the collision has enough energy for bonds to change. A gas-phase reaction between carbon monoxide and oxygen shows why orientation matters. The molecules can collide in more than one way. If the oxygen side of carbon monoxide...

arrhenius plots

Determining Activation Energy from Temperature

The Arrhenius equation links activation energy and the rate constant, k, for chemical reactions. It is written as k = Ae−Ea/RT. In this equation, R is the ideal gas constant with a value of 8.314 J/mol·K, T is the temperature on the kelvin scale, Ea is the activation energy in J/mole, e is the constant 2.7183, and A is the frequency factor. The frequency factor depends on collision frequency and the orientation of reacting molecules. Experimental kinetic data can be used to find the activation...

reaction mechanisms

Elementary Steps in Reaction Mechanisms

Chemical reactions can happen in steps, and a balanced equation does not show the full path at the molecular level. A reaction mechanism, also called a reaction path, gives the step-by-step process that explains how reactants become products. The decomposition of ozone is one example of a reaction that can be described by a sequence of steps. Each step in a mechanism is an elementary reaction. These elementary reactions happen in order, and when they are added together, they give the balanced...

rate-determining steps

Reaction Bottlenecks in Chemical Kinetics

Reaction bottlenecks help explain rate-determining steps in multistep reaction mechanisms. In a mechanism with several elementary steps, one step is often much slower than the others. That slowest step is called the rate-limiting step, or rate-determining step. A reaction cannot move faster than its slowest step, so this step controls the overall reaction rate. The idea is like traffic on a four-lane freeway with one lane closed. Cars can only move as fast as the bottleneck allows. In the same...

catalysis

Catalyst Action in Reaction Rates

Catalysts change the rate of a chemical reaction by giving it a faster path. A catalyst increases reaction rate without being consumed during the process. Its effect is often explained with reaction mechanisms and energy diagrams. For an endothermic reaction, the reactants and products start and end at the same energies in both cases. The uncatalyzed path is a one-step mechanism with one transition state. The catalyzed path follows a different mechanism with two transition states and a lower...

enzymes

Enzymes are biological catalysts that speed up many reactions in living organisms. They help control cellular metabolism by lowering the activation energy needed for biochemical reactions. When activation energy drops, reaction rates can increase. Enzyme problems can also lead to serious disease. A genetic abnormality that causes G6PD, or glucose-6-phosphate dehydrogenase, deficiency can disrupt the pathway that supplies NADPH to cells. In red blood cells, this can reduce glutathione and...

key terms and concepts

Explore how enzymes speed reactions, how active sites work, and how competitive and non-competitive inhibitors affect enzyme activity in high school biology.

Enzyme Action and Inhibition | JoVE K12

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

Pennsylvania State Academic Standards

Physical Science

Chemical Reactions

3.2.9-12.D

3.2.9-12.E

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Chemical reactions

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.f

Arizona Science Standards

High School

HS.P1

HS.P1U1.3

Next Generation Science Standards

Matter and Its Interactions

HS-PS1-4

HS-PS1-5

Florida Department of Education

SC.912.P.12

SC.912.P.12.12

Scientific Laws and Theories

Scientific Laws

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The Scientific Method

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Classifying Matter by State

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Classifying Matter by Composition

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The Atomic Theory of Matter

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Subatomic Particles

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Elements: Chemical Symbols and Isotopes

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Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

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Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

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Electronegativity values of ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

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lewis-structures-of-molecular-compounds-and-polyatomic-ions

Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Resonance

The Lewis structure of a nitrite anion (NO2&minus;) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O ...

Formal Charges

In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used to ...

Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

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, ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

comparing-intermolecular-forces-melting-point-boiling-point

Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

surface-tension-capillary-action-and-viscosity

Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded ...

Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

PS.Chm.3.2

Analyze the structure of atoms and isotopes.

Enzyme Action and Inhibition

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