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Encyclopedia > Electrochemical gradient

In cellular biology, an electrochemical gradient refers to the electrical and chemical properties across a membrane. These are often due to ion gradients, particularly proton gradients, and can represent a type of potential energy available for work in a cell. This can be calculated as a thermodynamic measure termed electrochemical potential that combines the concepts of energy stored in the form of chemical potential which accounts for an ion's concentration gradient across a cellular membrane and electrostatics which accounts for an ion's tendency to move relative to the membrane potential. Cell biology (cellular biology) is an academic discipline which studies the physiological properties of cells, as well as their behaviours, interactions, and environment; this is done both on a microscopic and molecular level. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Thermodynamics (Greek: thermos = heat and dynamic = change) is the physics of energy, heat, work, entropy and the spontaneity of processes. ... Electrochemical potential is a thermodynamic measure that reflects energy from entropy and electrostatics and is typically invoked in molecular processes that involve diffusion. ... In thermodynamics and chemistry, chemical potential, symbolized by μ, is a term introduced in 1876 by the American mathematical physicist (Willard Gibbs and his partner Lauren Berkley), which he defined as follows: Gibbs noted also that for the purposes of this definition, any chemical element or combination of elements in given... Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ... Membrane potential (or transmembrane potential or transmembrane potential difference or transmembrane potential gradient), is the electrical potential difference (voltage) across a cells plasma membrane. ...

Contents

Overview

Electrochemical potential is important in electroanalytical chemistry and industrial applications such as batteries and fuel cells. It represents one of the many interchangeable forms of potential energy through which energy may be conserved. To meet Wikipedias quality standards, this article or section may require cleanup. ... Conservation of energy states that the total amount of energy (often expressed as the sum of kinetic energy and potential energy) in an isolated system remains constant. ...


In biological processes the direction an ion will move by diffusion or active transport across membrane is determined by the electrochemical gradient. In mitochondria and chloroplasts, proton gradients are used to generate a chemiosmotic potential that is also known as a proton motive force. This potential energy is used for the synthesis of ATP by oxidative phosphorylation. This article or section does not cite its references or sources. ... This article or section does not cite its references or sources. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... The Electron Transport Chain. ...


An electrochemical gradient has two components. First, the electrical component is caused by a charge difference across the lipid membrane. Second, a chemical component is caused by a differential concentration of ions across the membrane. The combination of these two factors determines the thermodynamically favourable direction for an ions movement across a membrane. ...


Electrochemical gradients are analogous to hydroelectric dams and equivalent to the water pressure across the dam. Membrane transport proteins such as the sodium-potassium pump within the membrane are equivalent to turbines that convert the waters potential energy to other forms of physical or chemical energy, and the ions that pass through the membrane are equivalent to water that is now found at the bottom of the dam. Alternatively, energy can be used to pump water up into the lake above the dam. Similarly chemical energy in cells can be used to create electrochemical gradients. A transport protein is a protein involved in facilitated diffusion. ... The title given to this article is incorrect due to technical limitations. ...


Chemistry

The term is typically applied in contexts where a chemical reaction is to take place, such as one involving the transfer of an electron at a battery electrode. In a battery, an electrochemical potential arising from the movement of ions balances the reaction energy of the electrodes. The maximum voltage that a battery reaction can produce is sometimes called the standard electrochemical potential of that reaction (see also electrode potential and Table of standard electrode potentials). In instances pertaining specifically to the movement of electrically charged solutes, the potential is often expressed in units of volts. See: Concentration cell A chemical reaction occurs when vapours of hydrogen chloride and ammonia meet to form a cloud of a new substance, ammonium chloride Chemical reaction is a process that results in the interconversion of chemical substances [1]. The substance or substances initially involved in a chemical reaction are called reactants. ... This article or section does not cite its references or sources. ... This article may be too technical for most readers to understand. ... The values below are standard electrode potentials taken at 25°C in aqueous solution. ... Josephson junction array chip developed by NIST as a standard volt. ... A Concentration Cell is an electrochemical cell that has two equivalent half-cells of of the same material differing only in concentrations. ...


Biological context

In biology, the term is sometimes used in the context of a chemical reaction, in particular to describe the energy source for the chemical synthesis of ATP. More generally, however, it is used to characterize the inclined tendency of solutes to simply diffuse across a membrane, a process involving no chemical transformation. Adenosine 5-triphosphate (ATP), discovered in 1929 by Karl Lohmann,[1] is a multifunctional nucleotide primarily known in biochemistry as the molecular currency of intracellular energy transfer. ... Drawing of a cell membrane A cell membrane, plasma membrane or plasmalemma is a selectively permeable lipid bilayer coated by proteins which comprises the outer layer of a cell. ...


Ion gradients

With respect to a cell, organelle, or other subcellular compartments, the inclined tendency of an electrically charged solute, such as a potassium ion, to move across the membrane is decided by the difference in its electrochemical potential on either side of the membrane, which arises from three factors: Cells in culture, stained for keratin (red) and DNA (green). ... Schematic of typical animal cell, showing subcellular components. ... An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss (or addition) of an electron(s). ...

  • the difference in the concentration of the solute between the two sides of the membrane
  • the charge or "valence" of the solute molecule
  • the difference in voltage between the two sides of the membrane (i.e. the transmembrane potential).

A solute's electrochemical potential difference is zero at its "reversal potential". The transmembrane voltage to which the solute's net flow across the membrane is also zero. This potential is predicted theoretically either by the Nernst equation (for systems of one permeant ion species) or the Goldman-Hodgkin-Katz equation (for more than one permeant ion species). Electrochemical potential is measured in the laboratory and field using reference electrodes. In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ... In membrane biophysics sometimes used interchangeably with cell potential, but applicable to any lipid bilayer or membrane. ... Reversal potential is the following: In electrochemistry, reversal potential is the potential difference across a reversible cell. ... In electrochemistry, the Nernst equation gives the electrode potential (E), relative to the standard electrode potential, (E0), of the electrode couple or, equivalently, of the half cells of a battery. ... The Goldman-Hodgkin-Katz equation, more commonly known as the Goldman equation is used in cell membrane physiology to determine the potential across a cells membrane taking into account all of the ions that are permeant through that membrane. ... Reference electrode is an electrode which has a stable and well-known electrode potential. ...


Transmembrane ATPases or transmembrane proteins with ATPase domains are often used for making and utilizing ion gradients. The enzyme Na+/K+ ATPase use ATP to make a sodium ion gradient and a potassium ion gradient. The electrochemical potential is used as energy storage, chemiosmotic coupling is one of several ways a thermodynamically unfavorable reaction can be driven by a thermodynamically favorable one. Cotransport of ions by symporters and antiporter carriers are common to actively move ions across biological membranes. Na+/K+-ATPase (also known as the Na+/K+ pump or Na+/K+ exchanger) is an enzyme (EC 3. ... A symporter, also known as a coporter, is an integral membrane protein that is involved in facilitated diffusion. ... An antiporter is an integral membrane protein that is involved in secondary active transport. ...


Proton gradients

The proton gradient can be used as an intermediate energy storage for heat production and flagellar rotation. Additionally, it is an interconvertible form of energy in active transport, electron potential generation, NADPH synthesis, and ATP synthesis/hydrolysis. Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Adenosine 5-triphosphate (ATP), discovered in 1929 by Karl Lohmann,[1] is a multifunctional nucleotide primarily known in biochemistry as the molecular currency of intracellular energy transfer. ...


The electrochemical potential difference between the two sides of the membrane in mitochondria, chloroplasts, bacteria and other membranous compartments that engage in active transport involving proton pumps, is at times called a chemiosmotic potential or proton motive force (see chemiosmotic hypothesis). In this context, protons are often considered separately using units either of concentration or pH. In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... This article or section does not cite its references or sources. ... A proton pump is an integral membrane protein that is capable of moving protons across the membrane of a cell, mitochondrion, or other subcellular compartment, thereby creating a difference or gradient in both pH and electrical charge (ignoring differences in buffer capacity) and tending to establish an electrochemical potential. ... Peter D. Mitchell proposed the Chemiosmotic Hypothesis in 1961. ... Properties [1][2] In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... pH is a measure of the acidity of a solution in terms of activity of hydrogen ions (H+). For dilute solutions, however, it is convenient to substitute the activity of the hydrogen ions with the molarity (mol/L) of the hydrogen ions (however, this is not necessarily accurate at higher...


Proton Motive Force: two protons are expelled at each coupling site, generating the Proton Motive Force. ATP is made indirectly using the PMF as a source of energy. Eash pair of protons yield one ATP.


Some archaea, most notably halobacteria, make proton gradients by pumping in protons from the environment with the help of the solar driven enzyme bacteriorhodopsin, here it is used for driving the molecular motor enzyme ATP synthase to make the necessary conformational changes required to synthesize ATP. Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota Archaea (; from Greek αρχαία, old ones; singular Archaeum, Archaean, or Archaeon), also called Archaebacteria (), is a major division of living organisms. ... Genera Haloarcula Halobacterium Halobaculum Halococcus Haloferax Halogeometricum Halorubrum Haloterrigena Natrialba Natrinema Natronobacterium Natronococcus Natronomonas Natronorubrum The halobacteria are a family of archaea, found in water saturated or nearly saturated with salt. ... Bold textLink titleLink title Bacteriorhodopsin is the photosynthetic pigment used by archaea, most notably halobacteria. ... An ATP synthase (EC 3. ...


Proton gradients are also made by bacteria by running ATP synthase in reverse; this is used to drive flagellas.


The F1FO ATP synthase is a reversible enzyme. Large enough quantities of ATP cause it to create a transmembrane proton gradient. This is used by fermenting bacteria - which do not have an electron transport chain, and hydrolyze ATP to make a proton gradient - which they use for flagella and the transportation of nutrients into the cell. Properties [1][2] In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Horizontal line (use sparingly)d grade for the grade or gradient of roads and other geographic features. ... A flagellum (plural, flagella) is a whip-like organelle that many unicellular organisms, and some multicellular ones, use to move about. ...


In respiring bacteria under physiological conditions, ATP synthase generally runs in the opposite direction creating ATP while using the proton motive force created by the electron transport chain as a source of energy. The overall process of creating energy in this fashion is termed: oxidative phosphorylation. The same process takes place in mitochondria where ATP synthase is located in the inner mitochondrial membrane, so that F1-part sticks into mitochondrial matrix, where ATP synthesis takes place. The electron transfer chain (also called the electron transport chain, ETC, e-train, or simply electron transport), is any series of protein complexes and lipid-soluble messengers that convert the reductive potential of energized electrons into a cross-membrane proton gradient. ... The Electron Transport Chain. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ...


References

  • Campbell, Reece (2005). Biology. Pearson Benjamin Cummings. ISBN 0-8053-7146-X.
  • [1]

External links

See also


  Results from FactBites:
 
Electrochemical gradient - Wikipedia, the free encyclopedia (1011 words)
Electrochemical potential is important in electroanalytical chemistry and industrial applications such as batteries and fuel cells.
Electrochemical gradients are analogous to hydroelectric dams and equivalent to the water pressure across the dam.
Electrochemical potential is measured in the laboratory and field using reference electrodes.
Lecture 9, Electrochemical potential (803 words)
To describe this, we need a new term, the electrochemical potential of our charged species, defined as the sum of the chemical and electrical potentials for the component (see definitions of work terms in lecture 3).
Either a concentration gradient or a gradient in potential will favor transport, but the net gradient will be the sum of the chemical and electrical work terms.
Transport of protons is of particular importance in biological energy conversion, because the proton circuit couples the free energy changes of electron transfer reactions to the phosphorylation of ADP to ATP, through the proton gradient.
  More results at FactBites »

 
 

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