Name: measuring enzyme reaction rates
Uploaded: 2023-04-30T06:31:30.000Z
Duration: 8 min 7 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Physical Science

Matter and Its Interactions

HS-PS1-5

Enzyme Assays and Kinetics

ensayos enzimáticos y cinética

Cinética de la enzima describe los efectos catalíticos de las enzimas, que son biomoléculas que facilitan las reacciones químicas necesarias para los organismos vivos. Las enzimas actúan sobre moléculas, contempladas como sustratos a los productos de la forma. Parámetros cinéticos de la enzima se determinan mediante ensayos que directa o indirectamente medir los cambios en la concentración de substrato o producto con el tiempo.
Este video cubre los principios básicos de la cinética de la enzima (incluyendo las ecuaciones de velocidad) y modelos cinéticos. También se discuten los conceptos que rigen los ensayos enzimáticos, seguido por un típico análisis colorimétrico. Aplicaciones discute un análisis enzimático mediante el análisis de la transferencia (traste) de Förster Resonancia energética, caracterización de la actividad enzimática extracelular en el medio ambiente, y sondas de investigación ADN reparación cinética utilizando molecular.
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Las enzimas son catalizadores bioquímicos que son esenciales para la vida. Análisis de enzima se utilizan para estudiar las propiedades cinéticas de reacciones enzimáticas, elucidar los efectos catalíticos de las enzimas. Este video cubre cinética de la enzima y ensayos, pasar de un procedimiento general y mostrar algunas aplicaciones.
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Las enzimas son proteínas o moléculas similares a proteínas que actúan sobre una molécula de reactivo, conocida como el substrato. Las enzimas reducen la energía de activación de reacciones bioquímicas. Esto permite que las reacciones que se producen a mayor velocidad con menos requisitos de energía.
Reacciones enzimáticas pueden dividirse en tres componentes elementales. La primera es la formación de la enzima-sustrato complejo, formado por la Unión del sustrato al sitio activo de enzima. El complejo puede descomponerse en sus componentes originales. Esta es la segunda reacción elemental. Alternativamente, el complejo puede formar el producto y recuperar la enzima, la tercera reacción elemental.
La cinética de una reacción elemental es dada por la ecuación de la ley de tasa primaria. Ecuaciones de la ley de velocidad dan la tasa en términos de la concentración de los reactivos y una constante de velocidad. Cada una de las reacciones elementales tiene una ecuación de la ley de tarifa por persona, con su propia constante de velocidad. Estas ecuaciones pueden ser destiladas a un modelo cinético que se conoce como la ecuación de Michaelis-Menten. Esto le da la velocidad de reacción en términos de la concentración de sustrato; que puede ser determinada experimentalmente. Algunas tendencias generales de reacciones enzimáticas pueden ser identificados utilizando la ecuación de Michaelis-Menten. A concentración de sustrato alta, un punto de saturación se alcanza, llama Vmax. Aquí, la velocidad está limitada por la concentración total de enzima, y el número de moléculas de sustrato una enzima convierte en producto por momento, también conocido como kcat. De Michaelis-Menten cinética kcat es una de las dos constantes que rigen la velocidad de reacción. La constante KM, es conocida como la constante de afinidad. KM es también equivalente a la concentración donde la velocidad de reacción es equivalente a la mitad de la Vmax. Una enzima con una afinidad más alta tendrá una KM baja y llegar a la Vmax más rápido, mientras que una enzima con baja afinidad se tiene un alto KM y tardan más en llegar a la Vmax. Saber kcat y KM permite enzimas para compararse. Para ello utilizamos un ratio denominado eficiencia enzimática. Kcat mayor y menor KM como resultado una mayor eficiencia, menor kcat y más resultados KM en bajo.
Los factores utilizados para dilucidar la cinética de la enzima deben ser determinados experimentalmente. Estos ensayos se realizan típicamente mediante la mezcla de una solución de enzima y de sustrato en un ambiente controlado. Se realizan observaciones, midiendo los cambios en la concentración del sustrato, productos o subproductos con respecto al tiempo.
El cambio en la concentración con el tiempo se utiliza para determinar la velocidad de reacción. Para determinar la cinética, tarifa de datos se debe obtener en varias concentraciones. Si una parcela de la tasa inicial inversa vs concentración inicial inversa, conocido como el diagrama de Lineweaver-Burk, es lineal, entonces la reacción sigue la cinética de Michaelis-Menten. La pendiente y el intercepto de la línea permiten la determinación de los parámetros cinéticos KM y Vmax, que luego puede utilizarse para calcular kcat y la eficacia de la enzima.
Ahora que se han discutido los principios de la cinética de la enzima, echemos un vistazo a cómo se realiza un análisis de enzima típica.
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En este procedimiento se demuestra un análisis colorimétrico. El primer paso es generar una curva estándar, que se correlaciona la absorbancia con la concentración de proteína. Soluciones de concentración conocida se preparan junto con una muestra de control. Se añade una solución de revelador que reacciona con la proteína diana para producir un compuesto coloreado. La absorbancia es medida y conspiró contra la concentración para generar la curva estándar.
Para realizar el ensayo, se prepara una concentración conocida de sustrato junto con la cantidad adecuada de enzimas. El enzima y el substrato se mezclan y permitió a incubar durante un intervalo de tiempo. pH y la temperatura se controlan con soluciones tampón y bloques de calefacción. Se agrega un agente de amortiguamiento para detener la reacción. Solución de revelado entonces se añade a las reacciones y mezclado. Las soluciones se colocan en cubetas y se mide la absorbancia. La cantidad de sustrato consumido se determina mediante la comparación de la absorbancia medida a la curva estándar. Utilizando los datos recogidos, se determinan velocidades de reacción inicial de concentración con el tiempo. Finalmente, con la tarifa de datos y la concentración, se hace la trama de Michaelis-Menten. Esto permite la determinación de las propiedades cinéticas de la enzima como número y enzima la eficiencia de facturación.
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Ahora que hemos revisado un procedimiento de análisis, veamos otras formas se realizan ensayos y sus aplicaciones.
En este procedimiento traste análisis se utilizan para estudiar la cinética de una proteasa hidrolizando un enlace peptídico de una proteína. Estas emisiones pueden medirse, lo que permite un análisis continuo y cuantitativo de la producción y el consumo de sustrato, ayudar en la determinación de la cinética de la reacción.
Análisis de enzima se pueden utilizar en ciencias ambientales para determinar los niveles de actividad enzimática extracelular en el medio ambiente. Aguas, suelos y sedimentos pueden recogidos del ambiente y procesados en el laboratorio. Actividad enzimática extracelular de estos materiales se puede caracterizar entonces mediante pruebas enzimáticas. Se trata de una herramienta útil para la comprensión de cómo el medio ambiente procesos de material orgánico.
Mecanismo de reparación de ADN de una célula puede evaluarse mediante el estudio de la cinética de enzimas encontradas en el núcleo. La tasa en la que una enzima elimina daños, o lesiones del ADN puede medirse utilizando balizas moleculares fluorescentes, que sólo es fluorescente cuando ligada a secuencias de ADN únicas. El nivel de reparación del ADN se puede medir en tiempo real mediante la detección de los productos de fluorescencia marcado escote.
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Sólo ha visto vídeo de Zeus sobre la cinética de la enzima y ensayos. Este video explica la cinética de la enzima abarcado conceptos de análisis, fue un procedimiento general y describe algunas aplicaciones.
¡Gracias por ver!
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Ensayos enzimáticos y cinética

Enzyme kinetics describes the catalytic effects of enzymes, which are biomolecules that facilitate chemical reactions necessary for living organisms. ...

Las enzimas son catalizadores bioquímicos esenciales para la vida. Los ensayos enzimáticos se utilizan para estudiar las propiedades cinéticas de las reacciones enzimáticas, dilucidando los efectos catalíticos de las enzimas. Este video cubrirá la cinética y los ensayos de enzimas, repasará un procedimiento general y mostrará algunas aplicaciones. Las enzimas son proteínas, o con menos frecuencia ARN, que actúan sobre un reactivo específico, denominado sustrato. Una enzima reduce la energía de activación necesaria para iniciar una reacción bioquímica, lo que hace que la reacción ocurra a un ritmo más rápido. Las reacciones enzimáticas se pueden dividir en tres componentes elementales. La primera es la formación del complejo enzima-sustrato, formado por la unión del sustrato al sitio activo de la enzima. El complejo puede descomponerse en sus componentes originales. Esta es la segunda reacción elemental. Alternativamente, el complejo puede formar el producto y recuperar la enzima, la tercera reacción elemental. La cinética de una reacción elemental viene dada por la ecuación de la ley de la tasa elemental. Las ecuaciones de la ley de velocidad dan la tasa en términos de la concentración de los reactivos y una constante de velocidad. Cada una de las reacciones elementales tiene una ecuación de ley de velocidad individual, con su propia constante de velocidad. Estas ecuaciones se pueden resumir en un modelo cinético conocido como la ecuación de Michaelis-Menten. Esto da la velocidad de reacción en términos de la concentración de sustrato; que se pueden determinar experimentalmente. Algunas tendencias generales de las reacciones enzimáticas se pueden identificar utilizando la ecuación de Michaelis-Menten. A una alta concentración de sustrato, se alcanza un punto de saturación, llamado Vmax. Aquí, la tasa está limitada por la concentración total de la enzima y el número de moléculas de sustrato que una enzima convierte en producto en un tiempo dado, también conocido como kcat. En la cinética de Michaelis-Menten, kcat es una de las dos constantes que gobiernan la velocidad de reacción. La otra constante, KM, se conoce como constante de afinidad. KM también es equivalente a la concentración donde la velocidad de reacción es equivalente a medio Vmax . Una enzima con una mayor afinidad tendrá un KM más bajo y alcanzará la Vmax más rápido, mientras que una enzima con una afinidad más baja tendrá un KM más alto y tardará más en alcanzar la Vmax. Conocer kcat y KM permite comparar enzimas. Para ello, utilizamos una relación llamada eficiencia enzimática. Un kcat más alto y un KM más bajo dan como resultado eficiencias más altas, mientras que un kcat más bajo y un KM más alto dan como resultado una menor productividad. Los factores utilizados para dilucidar la cinética de las enzimas deben determinarse experimentalmente. Estos ensayos generalmente se realizan mezclando una solución de enzima y sustrato en un entorno controlado. Las observaciones se realizan midiendo los cambios en la concentración del sustrato, producto o subproductos con respecto al tiempo. El cambio en la concentración a lo largo del tiempo se utiliza para determinar la velocidad de reacción. Para determinar la cinética, se deben obtener datos de dosis a múltiples concentraciones. Si un gráfico de la tasa inicial inversa frente a la concentración inicial inversa, conocido como el diagrama de Lineweaver-Burk, es lineal, entonces la reacción sigue la cinética de Michaelis-Menten. La pendiente y la intersección de la línea permiten la determinación de los parámetros cinéticos KM y Vmax, que luego se pueden utilizar para calcular kcat y la eficiencia de la enzima. Ahora que se han discutido los principios de la cinética de las enzimas, veamos cómo se realiza un ensayo enzimático típico. En este procedimiento se demuestra un ensayo colorimétrico. ? El primer paso es generar una curva estándar, que correlacionará la absorbancia con la concentración de sustrato. Las soluciones de concentración conocida se preparan junto con una muestra de control. Se añade una solución reveladora que reacciona con el sustrato para producir un compuesto coloreado. La absorbancia se mide y se traza en función de la concentración para generar la curva estándar. Para realizar el ensayo, se prepara una concentración conocida de sustrato junto con la cantidad adecuada de enzima. La enzima y el sustrato se mezclan y se dejan incubar durante un intervalo de tiempo determinado. El pH y la temperatura se controlan con soluciones tampón y bloques calefactores. Se agrega un agente de enfriamiento para detener la reacción. A continuación, se añade una solución de revelador a las reacciones y se mezcla. A continuación, las soluciones se colocan en cubetas y se mide la absorbancia. La cantidad de sustrato consumido se determina comparando la absorbancia medida con la curva estándar. Con los datos recopilados, las velocidades de reacción iniciales se determinan trazando la concentración a lo largo del tiempo. Finalmente, con los datos de tasa y concentración, se realiza el diagrama de Michaelis-Menten. Esto permite determinar las propiedades cinéticas de la enzima, como el número de rotación y la eficiencia de la enzima. Ahora que hemos revisado un procedimiento de ensayo, veamos otras formas en que se realizan los ensayos y sus aplicaciones. En este procedimiento, el análisis FRET se utiliza para estudiar la cinética de una proteasa que hidroliza un enlace peptídico de una proteína. Estas emisiones se pueden medir, lo que permite un análisis continuo y cuantitativo del consumo y la producción de sustrato, lo que ayuda a determinar la cinética de la reacción. Los ensayos enzimáticos se pueden utilizar en ciencias ambientales para determinar los niveles de actividad enzimática extracelular en el medio ambiente. Las aguas, los suelos y los sedimentos pueden recogerse del medio ambiente y procesarse en el laboratorio. La actividad enzimática extracelular de estos materiales se puede caracterizar mediante ensayos enzimáticos. Esta es una herramienta útil para comprender cómo el medio ambiente procesa la materia orgánica. El mecanismo de reparación del ADN de una célula se puede evaluar mediante el estudio de la cinética de las enzimas que se encuentran en el núcleo. La velocidad a la que una enzima elimina las lesiones o daños en el ADN se puede medir utilizando balizas moleculares fluorescentes, que solo emiten fluorescencia cuando se unen a secuencias de ADN únicas. El nivel de reparación del ADN se puede medir en tiempo real mediante la detección de los productos de escisión marcados con fluorescencia. Acabas de ver el vídeo de JoVE sobre la cinética y los ensayos enzimáticos. Este video explicó la cinética de las enzimas, cubrió los conceptos de los ensayos, repasó un procedimiento general y describió algunas aplicaciones. ¡Gracias por mirar!

Education

Educación

JoVE Science Education

Chemistry

Química

Biochemistry

Bioquímica

measuring enzyme reaction rates

Enzyme reaction rates can be measured with assays that track how substrate or product levels change over time. Enzymes are proteins, or sometimes RNAs, that speed up chemical reactions by lowering the activation energy needed to start them. They act on a specific substrate and help form a product that supports life processes.

Enzymatic reactions are often described in three steps. First, the substrate binds to the enzyme active site and forms an enzyme-substrate complex. That complex can fall apart again, or it can make product and release the enzyme. Each step has its own rate law and rate constant.

These steps are often simplified with the Michaelis-Menten equation. This model links reaction rate to substrate concentration and helps show general enzyme trends. At high substrate levels, the reaction reaches a saturation point called V max. The turnover number, or k cat, describes how many substrate molecules one enzyme converts per unit time. KM is the concentration where the rate is half of V max, and it also reflects affinity. A lower KM usually means higher affinity, while a higher KM usually means lower affinity. The ratio of k cat and KM is used as enzyme efficiency.

To find these values, scientists run assays in a controlled setting. They mix enzyme and substrate and measure changes in substrate, product, or byproducts over time. Reaction rates are collected at multiple substrate concentrations. If a Lineweaver-Burk plot, which graphs inverse initial rate against inverse initial concentration, is linear, the reaction follows Michaelis-Menten kinetics. The slope and intercept can then be used to determine KM and V max, and these values help calculate k cat and enzyme efficiency.

A common lab method is a colorimetric assay, which uses color to measure concentration. First, a standard curve is made from known concentrations and a control sample. A developer solution reacts with the substrate and creates a colored compound. Absorbance is measured and plotted against concentration to build the curve.

For the assay, a known amount of substrate and enzyme is prepared. The two are mixed and incubated for a set time. Buffer solutions and heating blocks keep pH and temperature controlled. A quenching agent stops the reaction, and developer solution is added. The samples are placed in cuvettes, and absorbance is measured. The amount of substrate used is found by comparing the result to the standard curve. Initial rates are then plotted over time, and the Michaelis-Menten plot is used to determine turnover number and enzyme efficiency.

Other assay methods can track reactions in real time. FRET, or Förster resonance energy transfer, can measure a protease breaking a peptide bond in a protein. The emitted signal can be monitored continuously, which helps quantify substrate consumption and product formation. Enzyme assays are also used in environmental science to measure extracellular enzyme activity in waters, soils, and sediments. These samples are processed in the lab to help explain how the environment breaks down organic material.

Enzyme kinetics can also be used to study DNA repair. Enzymes in the nucleus remove DNA lesions, or damage, and their activity can be followed with fluorescent molecular probes. These beacons fluoresce only when they bind specific DNA sequences. The fluorescent cleavage products make it possible to measure DNA repair in real time.

Measuring Enzyme Reaction Rates

dialysis: diffusion based separation

Dialysis for Buffer Exchange in Biochemistry

Dialysis is a common biochemistry technique for buffer exchange and desalting. It separates molecules by diffusion through a semipermeable membrane, which lets small molecules pass while holding larger biomolecules inside the sample. The membrane is the key part of the setup. Its pores create a molecular weight cutoff, so a membrane such as a 10 kDa membrane usually keeps molecules larger than 10 kilodaltons inside. This cutoff is not exact, because membranes have a range of pore sizes.

enzyme assays and kinetics

Enzyme reaction rates can be measured with assays that track how substrate or product levels change over time. Enzymes are proteins, or sometimes RNAs, that speed up chemical reactions by lowering the activation energy needed to start them. They act on a specific substrate and help form a product that supports life processes. Enzymatic reactions are often described in three steps. First, the substrate binds to the enzyme active site and forms an enzyme-substrate complex. That complex can fall...

maldi-tof mass spectrometry

How MALDI-TOF Reads Biomolecules

MALDI-TOF mass spectrometry reads biomolecules by using a laser, a matrix, and a time-of-flight analyzer. MALDI, or matrix-assisted laser desorption ionization, helps fragile molecules keep their structure while they are moved into the mass analyzer. The analyzer then separates compounds based on size and charge. In MALDI, the sample is mixed into a matrix, usually an organic compound with aromatic and conjugated double bonds. A laser pulse strikes the spot, and the matrix absorbs most of the...

tandem mass spectrometry

Tandem Mass Spectrometry for Biomolecule Analysis

Tandem mass spectrometry is used to isolate a biomolecule and break it into smaller pieces so its makeup can be studied. Because biomolecules often have large, complex structures, it can be hard to identify their molecular composition and sequence from a single measurement. By linking mass spectrometers in series, the technique first selects one ion and then analyzes the fragments it produces. The process starts with an ion source that converts the sample into ions. A mass analyzer then...

protein crystallization

Protein Crystals for Structure Analysis

Protein crystals help scientists study protein structure and function. A crystal is a solid lattice made from purified protein molecules. These crystals are useful in structural biology because they reveal details that methods like mass spectrometry and SDS-PAGE cannot show on their own. Protein crystallization is paired with recombinant protein expression and x-ray diffraction to support this work. The process starts with a large amount of very pure protein. Researchers often make that...

chromatography-based biomolecule purification methods

chromatography-based-biomolecule-purification-methods

Protein Purification with SEC and IMAC

Protein purification with size-exclusion chromatography and affinity chromatography helps isolate biomolecules from complex mixtures. These methods are common in biochemistry because purified samples are needed before a biomolecule’s properties and activity can be studied. The video focuses on the principles behind size-exclusion chromatography, affinity chromatography, and immobilized metal affinity chromatography, or IMAC. Size-exclusion chromatography, or SEC, separates molecules by size. A...

two-dimensional gel electrophoresis

Protein Mapping with 2D Gel Electrophoresis

Protein mapping with 2D gel electrophoresis separates complex protein mixtures across two steps. The method combines isoelectric focusing, or IEF, with sodium dodecyl sulfate polyacrylamide gel electrophoresis, or SDS-PAGE. Together, these methods can resolve thousands of biomolecules from a single sample by their isoelectric point and molecular weight. The first dimension is IEF. Each protein has an isoelectric point, or pI, which is the pH where its net charge is zero. Proteins are loaded...

metabolic labeling

Tracking Cell Chemistry with Metabolic Labels

Metabolic labeling tracks cell chemistry by using chemical analogs that cells take up and build into biomolecules. These labels help scientists follow biochemical changes and modifications inside cells. The labeled products can then be studied with tools such as SDS-PAGE and NMR to learn more about metabolic pathways. Several labeling strategies are shown here. Isotopic labeling uses analogs that match the natural molecule but contain uncommon isotopes, such as carbon-13 and nitrogen-15 in an...

electrophoretic mobility shift assay (emsa)

electrophoretic-mobility-shift-assay-emsa

Detecting Protein-DNA Binding by EMSA

Electrophoretic mobility shift assay, or EMSA, is a biochemical method used to detect binding between proteins and nucleic acids. It is also called a gel shift assay. The test compares how a labeled nucleic acid moves through a gel before and after it binds a protein. EMSA is used to see whether a specific protein binds to a specific nucleic acid. First, the nucleic acid is labeled to make a probe. The transcript describes radioactive phosphorus-32 as a common label. The probe is then mixed...

photometric protein determination

Measuring Protein Concentration with Absorbance

Measuring protein concentration with absorbance is a key step in many biochemical assays. Photometric methods use the fact that samples with more light-absorbing material transmit less light. Because concentration and absorption are directly related, this makes it possible to measure an unknown sample. The core idea comes from the Beer-Lambert Law. This law states that the concentration of a light-absorbing species is proportional to its absorbance. The video also introduces the Bradford assay...

density gradient ultracentrifugation

Sucrose Gradient Separation in an Ultracentrifuge

Sucrose gradient separation in an ultracentrifuge is a lab method for isolating cell parts and biomolecules. It uses differences in density to make particles sink or rise in a liquid. A high-speed ultracentrifuge speeds up this process so components can be separated without destroying them. The basic idea starts with a suspension, which is particles mixed in a liquid solvent. Particles that are denser than the solvent sediment, while less dense particles float. A rotor inside the...

co-immunoprecipitation and pull-down assays

co-immunoprecipitation-and-pull-down-assays

Protein Interaction Capture Methods in Cells

Co-immunoprecipitation and pull-down assays are laboratory methods used to capture stable protein-protein interactions. Protein-protein interactions help control many biological functions, but many of them have not yet been identified. These assays are related to immunoprecipitation, which isolates a target protein from a mixed sample using an antibody. In co-immunoprecipitation, or CoIP, an antibody binds the target protein, and that protein is already attached to another protein that the...

reconstitution of membrane proteins

Membrane Proteins in Liposome Models

Membrane proteins can be moved into liposome models so their function can be studied outside a cell. Reconstitution means restoring an isolated biomolecule to a working form. For membrane proteins, that usually means placing a purified protein into an artificial lipid membrane. Cell membranes are made mainly of phospholipids and membrane proteins. The phospholipids form a bilayer with hydrophilic phosphate heads facing water and hydrophobic fatty acid tails facing inward. Some membrane...

f&#246;rster resonance energy transfer (fret)

FRET as a Molecular Ruler in Cells

Föster resonance energy transfer, or FRET, is a way to study close-range biochemical interactions using light-emitting molecules. A donor fluorophore can pass energy to an acceptor fluorophore when their emission and absorption spectra overlap. This transfer happens only when the pair is very close together, usually within 10 nm. Because FRET depends on distance, it is often called a molecular or spectroscopic ruler. The strength of the signal is measured as FRET efficiency, which describes...

surface plasmon resonance (spr)

SPR Biosensors for Tracking Binding Kinetics

Surface plasmon resonance, or SPR, is a way to track biomolecular binding on a label-free biosensor. It is used to measure molecular affinity, kinetics, specificity, and concentration. The method works with a thin metal layer on a prism, where changes in reflected light reveal interactions in real time. SPR sensors use a thin layer of a noble metal on the face of a prism. Light is reflected from the prism-metal interface into a photodetector. At one specific angle, called the surface plasmon...

biochemistry

Esta colección presenta varios métodos de purificación comúnmente usados, como la cromatografía de afinidad y métodos analíticos, como MALDI-TOF. Además, los videos muestran métodos para evaluar la interacción y la función de diversas biomoléculas como en la coprecipitación y el etiquetado metabólico.

Measure enzyme reaction rates with assays, standard curves, and Michaelis-Menten plots. Learn how kcat, KM, colorimetric assays, FRET, and DNA repair studies work.

Measuring Enzyme Reaction Rates | JoVE K12

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-5.

Life Science

Structure and Function

HS-LS1-1.

matter-and-energy-in-organisms-and-ecosystems

Matter and Energy in Organisms and Ecosystems

HS-LS1-6.

Inheritance and Variation of Traits

HS-LS3-1.

Overveiw

Principles of Enzyme Kinetics

Enzyme Assay

Applications

Summary

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Atomic Structure

All matter is composed of atoms, the smallest individual units of elements. Each atom is made up of three subatomic particles: protons, neutrons, and ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Electronic Structure of Atoms


An atom comprises protons and neutrons, which are contained inside the dense, central&#160;core called the nucleus, with electrons present around the ...

Electron Behavior

Electrons are negatively charged subatomic particles that are attracted to an orbit around the positively-charged nucleus of an atom. They reside in ...

Electron Orbital Model

Orbitals are the areas outside of the atomic nucleus where electrons are most likely to reside. They are characterized by different energy levels, shapes, ...

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 Configurations

Electron configurations and orbital diagrams can be determined by applying the Aufbau principle (each added electron occupies the subshell of lowest ...

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 ...

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 ...

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 ...

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 ...

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Halogens

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. ...

Noble Gases


The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name &ldquo;noble&rdquo; because they were ...

Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms. [Clarification Statement: Examples of properties that could be predicted from patterns could include reactivity of metals, types of bonds formed, numbers of bonds formed, and reactions with oxygen.] [Assessment Boundary: Assessment is limited to main group elements. Assessment does not include quantitative understanding of ionization energy beyond relative trends.]

HS-PS1-1

Atomic Number and Mass Number

The number of protons in the nucleus of an atom is its atomic number (Z). This is the defining trait of an element. Its value determines the identity of ...

Chemical Reactions

A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or ...

Chemical Equations

Chemical equations represent the identities and relative quantities of substances involved in a chemical reaction. The substances undergoing reaction are ...

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Predicting Reaction Outcomes

Kinetics describes the rate and path by which a reaction occurs. In contrast, thermodynamics deals with state functions and describes the properties, ...

Chemical Reactions in Aqueous Solutions

Chemical substances interact in many different ways. Certain chemical reactions exhibit common patterns of reactivity. Due to the vast number of chemical ...

Multi-Step Reactions

Chemical reactions often occur in a stepwise fashion involving two or more distinct reactions taking place in a sequence. A balanced equation indicates ...

Reaction Mechanisms

Chemical reactions often occur in a stepwise fashion, involving two or more distinct reactions taking place in a sequence. A balanced equation indicates ...

Rate-Determining Steps

Relating Reaction Mechanisms
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest ...

Reaction Stoichiometry

A balanced chemical equation provides a great deal of information in a very succinct format. Chemical formulas provide the identities of the reactants and ...

Limiting Reactant

The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as stoichiometric amounts. However, in ...

Reaction Yield

The theoretical yield of a reaction is the amount of product estimated to form based on the stoichiometry of the balanced chemical equation. The ...

stoichiometry-product-yield-and-limiting-reactants

Stoichiometry, Product Yield, and Limiting Reactants

Chemical equations represent how a chemical reaction proceeds from reactants to products through physical or chemical change using chemical formulas.
...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Preparation of 25% v/v Ethylenediamine in Deionized WaterExpand
	Here, we show the laboratory ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

	Synthesis of tris(ethylenediamine)nickel chlorideExpand
	In this lab, you will combine nickel ...

Balancing Redox Equations

Electrochemistry is the science involved in the interconversion of electrical and chemical reactions. Such reactions are called reduction-oxidation, or ...

Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties. [Clarification Steatement: Examples of chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen, or of carbon and hydrogen.] [Assessment Boundary: Assessment is limited to chemical reactions involving main group elements and combustion reactions.]

HS-PS1-2

What is Matter?

The substance of the universe&#8212;from a grain of sand to a star&#8212;is called matter. Scientists define matter as anything that occupies space and ...

Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles. [Clarification Statement: Emphasis is on understanding the strengths of forces between particles, not on naming specific intermolecular forces (such as dipole-dipole). Examples of particles could include ions, atoms, molecules, and networked materials (such as graphite). Examples of bulk properties of substances could include the melting point and boiling point, vapor pressure, and surface tension.] [Assessment Boundary: Assessment does not include Raoult’s law calculations of vapor pressure.]

HS-PS1-3

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

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, ...

Bonding in Metals

Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Dr&#xFC;de called the ...

types-of-chemical-reactions-anabolic-and-catabolic

Types of Chemical Reactions: Anabolic and Catabolic

The first law of thermodynamics holds that energy can neither be created nor destroyed&#8212;it can only change form. An organism&#39;s essential function ...

types-of-chemical-reactions-exchange-and-reversible

Types of Chemical Reactions: Exchange and Reversible

An exchange reaction is a chemical reaction in which both synthesis and decomposition occur, chemical bonds are both formed and broken, and chemical ...

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 ...

Arrhenius Plots

The Arrhenius equation relates the activation energy and the rate constant, k, for chemical reactions. In the Arrhenius equation, k = Ae&#8722;Ea/RT, R is ...

Reaction Rate

The rate of reaction is the change in the amount of a reactant or product per unit time. Reaction rates are therefore determined by measuring the time ...

Measuring Reaction Rates

Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical ...

factors-influencing-the-rate-of-chemical-reactions

Factors Influencing the Rate of Chemical Reactions

A variety of factors influence the rate of chemical reactions. For a chemical reaction to happen, atoms must collide with enough energy to overcome the ...

Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy. [Clarification Statement: Emphasis is on the idea that a chemical reaction is a system that affects the energy change. Examples of models could include molecular-level drawings and diagrams of reactions, graphs showing the relative energies of reactants and products, and representations showing energy is conserved.] [Assessment Boundary: Assessment does not include calculating the total bond energy changes during a chemical reaction from the bond energies of reactants and products.]

HS-PS1-4

Measuring Enzyme Reaction Rates

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