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Topic: Chemiosmotic potential

	Chemiosmotic hypothesis - Wikipedia, the free encyclopedia
		The Chemiosmotic Hypothesis is the proposal in 1961, by Peter D. Mitchell, that the mitochondrion functioned as a kind of electrochemical capacitor, using the energy of NADH and FADH
		The problem with the older paradigm is that no high energy intermediate was ever found, and the evidence for proton pumping by the complexes of the electron transfer chain grew too great to be ignored.
		Eventually the weight of evidence began to favor the chemiosmotic hypothesis, and in 1978, Peter Mitchell was awarded the Nobel Prize in Chemistry.
	en.wikipedia.org /wiki/Chemiosmotic_hypothesis (197 words)

	CONK! Encyclopedia: Proton_gradient (Site not responding. Last check: 2007-10-22)
		The chemiosmotic 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, I.E by letting the ions diffuse through the high concentration side to the low concentration side through transmembrane proteins which can use them as energy.
		Additionally it is an interconvertible form of energy in active transport, electron potential generation, NADPH synthesis and ATP synthesis/hydrolysis.
		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.
	www.conk.com /search/encyclopedia.cgi?q=Proton_gradient (347 words)

	Electrochemical potential -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-22)
		In biology too the term is sometimes used in the context of a chemical reaction, in particular to describe the energy source for the chemical synthesis of (A nucleotide derived from adenosine that occurs in muscle tissue; the major source of energy for cellular reactions) ATP.
		A solute's electrochemical potential difference is zero at its " (Click link for more info and facts about reversal potential) reversal potential", the transmembrane voltage at which the solute's net flow across the membrane is zero.
		This potential is predicted theoretically either by the (Click link for more info and facts about Nernst equation) Nernst equation (for systems of one permeant ion species) or the Goldman-Hodgkin-Katz equation (for more than one permeant ion species).
	www.absoluteastronomy.com /encyclopedia/e/el/electrochemical_potential.htm (429 words)

	Electrochemical potential (Site not responding. Last check: 2007-10-22)
		Electrochemical potential is a thermodynamic measure that reflects energy from entropy and electric charge and is typically invoked in molecule processes that involve diffusion.
		It represents one of many interchangeable forms of potential energy through which energy may be conservation of energy.
		The electrochemical potential difference between the two sides of the membrane in mitochondria, chloroplasts, bacterium and other membranous compartments that engage in active transport involving proton pumps, is at times called a chemiosmotic potential (see chemiosmotic hypothesis).
	read-and-go.hopto.org /Thermodynamics/Electrochemical-potential.html (424 words)

	Thermosynthesis Niches in the Solar System
		The oriented molecules of the monolayer constitute a dipole layer; the associated dipole potential is easily measured.
		Their difference in dipole potentials results in a membrane dipole potential that will change during a thermotropic phase transition.
		During thermal cycling the membrane potential varies just as during light/dark cycling in PS0, and ATP can be gained similarly to PS0, using the same ATPsynthase.
	www.geocities.com /ResearchTriangle/Node/5345/html_files/postjul99.html (2535 words)

	BIFC 3521: Lecture
		The redox potential for a half reaction is determined by comparing that half reaction to a standard half reaction.
		The chemiosmotic hypothesis proposes that the free energy of electron transport is conserved by pumping protons from the mitochondrial matrix to the intermembrane space so as to create an electrochemical proton gradient across the inner mitochondrial membrane.
		The electrochemical potential of this gradient is harnessed to synthesize ATP.
	www.library.csi.cuny.edu /~davis/Biochem_3521/lect19_20/lect19.html (4443 words)

	Inorganic Cation Transport and Energy Transduction in Enterococcus hirae and Other Streptococci -- Kakinuma 62 (4): ...
		Generation of the proton potential is one of the major functions of the streptococcal F
		symport of a metabolite with one proton, a proton potential of
		accumulation was observed in the absence of a proton potential.
	mmbr.asm.org /cgi/content/full/62/4/1021 (8799 words)

	Biological Oxidations
		Because it is not practical to measure electron concentrations directly, the electron energy potential of a redox system is determined from the electrical potential or voltage of the individual half cells, relative to a standard half cell.
		By convention, standard electrode potentials are written as potentials for reduction reactions of half cells.
		This potential is the sum of the concentration difference of protons across the membrane and the difference in electrical charge across the membrane.
	www.dentistry.leeds.ac.uk /biochem/thcme/oxidative-phosphorylation.html (3146 words)

	Mitochondria function: the chemiosmotic gradient
		The efficiency of electron transport can be represented by the standard reduction potential difference, namely the voltage generated by a redox reaction under standard biochemical conditions.
		The standard reduction potential of NADH is -0.315V, while that of coenzyme Q is 0.045V (difference of 0.345 V).
		Even in the presence of ADP, which allows ATP synthetase to exploit the gradient, the chemiosmotic gradient is maintained at a set energy level.
	www.ruf.rice.edu /~bioslabs/studies/mitochondria/mitogradient.html (1543 words)

	H+/ATP ratio of proton transport-coupled ATP synthesis and hydrolysis catalysed by CF0F1[ndash]liposomes (Site not responding. Last check: 2007-10-22)
		In this work, we describe a new method and an ideal chemiosmotic system to determine this ratio for CF Isolated, purified CF was reconstituted into liposomes prepared from phosphatidylcholine/phosphatidic acid, and the rates of ATP synthesis and ATP hydrolysis were measured with luciferin/luciferase.
		In this system, the compositions of the internal and external phase were known exactly; in particular, the internal pH could be measured with a glass electrode due to equilibration of the internal phase with the incubation solution during reconstitution.
		According to the chemiosmotic theory, the coupling of ATP synthesis and ATP hydrolysis with the transmembrane proton transport is described by equation 1:
	www.nature.com /cgi-taf/dynapage.taf?file=/emboj/journal/v22/n3/full/7594982a.html (6396 words)

	Chapter 18 : Oxidative Phosphorylation and Photophosphorylation (Site not responding. Last check: 2007-10-22)
		Indirect measurements of the transmembrane electrical potential in respiring mitochondria yield a value of 0.1 to 0.2 V, inside negative.
		Chemiosmotic theory also accounts for a third condition that uncouples oxidation from phosphorylation-mechanical disruption of the mitochondrial membrane.
		The sum of the chemical potential provided by the pH difference and the electrical potential provided by the separation of charges is a proton-motive force large enough to support ATP synthesis in the absence of an oxidizable substrate.
	www.bioinfo.org.cn /book/biochemistry/chapt18/sim5.htm (2543 words)

	Kinetics of Electron Transfer through the Respiratory Chain -- Jin and Bethke 83 (4): 1797 -- Biophysical Journal
		is the electrochemical potential of each species i in the reaction.
		E is the difference in redox potential between the donating and accepting half-reactions
		is the difference in the standard redox potentials between the reactions, calculated at the standard state of interest,
	www.biophysj.org /cgi/content/full/83/4/1797 (4121 words)

	CHEMIOSMOTIC POTENTIAL (Site not responding. Last check: 2007-10-22)
		In electrochemistry, 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.
		With respect to a biological cell, organelle, or other subcellular compartment, the propensity 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:
		This potential is predicted theoretically by the Nernst equation, which applies generally to circumstances of electrodiffusion.
	www.websters-online-dictionary.org /definition/CHEMIOSMOTIC+POTENTIAL (390 words)

	A Proton Gradient Powers the Synthesis of ATP
		It was first suggested that electron transfer leads to the formation of a covalent high-energy intermediate that serves as a high phosphoryl transfer potential compound or to the formation of an activated protein conformation, which then drives ATP synthesis.
		As we calculated in Section 18.2.2, this membrane potential corresponds to a free energy of 5.2 kcal (21.8 kJ) per mole of protons.
		The entry of protons into the cytosolic half-channel is further facilitated by the membrane potential of +0.14 V (positive on the cytoplasmic side), which increases the concentration of protons near the mouth of the cytosolic half-channel.
	www.ncbi.nlm.nih.gov /books/bv.fcgi?call=bv.View..ShowSection&rid=stryer.section.2528 (2366 words)

	The ETC & Oxidative Phosphorylation (Site not responding. Last check: 2007-10-22)
		Although their existence had been questioned on the basis of light microscropy, there was no doubt about mitochondria when electron microsopy was applied to the subject in the 1940’s.
		The redox potential measures the tendancy for electrons to flow from a redox pair (referred to as a redox couple) to a standard (reference) redox couple which is H
		O half cell, and a standard state redox potential of +0.82 V would be recorded.
	www.botany.ubc.ca /teaching/biol201/201etc.htm (2217 words)

	Bioenergetics of the Archaea -- Schäfer et al. 63 (3): 570 -- Microbiology and Molecular Biology Reviews
		The membrane potential can contribute approximately 90% to the proton motive force (56) in methanogenic archaea also, as
		The top scheme illustrates the processes found in archaea that contribute to the formation of either proton or sodium ion potentials across the plasma membrane.
		One heme is a high-spin heme with a midpoint potential
	mmbr.asm.org /cgi/content/full/63/3/570 (7510 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		water “flow” can be regulated by osmotic potential, cell solute concentration, so if the solute concentration is altered in a cell than water movement and Turgor pressure can be affected.
		Consider: Diffusion vs long-distance transport; bulk flow in soil then more complicated (combination of factors account for it) Apoplastic vs symplastic movement (caspariam strip — suberized strip at the endodermis) Root uptake by osmosis and mass flow driven by xylem pressure which is related to transpiration (E), keeps the water moving.
		Tracheary Elements: tracheids and vessel elements, 4.7 and 4.8 in text, dead when functional, no membranes or organelles Tracheids: angiosperms and gymnosperms, communication is lateral via pit pairs.
	www.nrsl.umd.edu /courses/nrsc484/water.doc (497 words)

	World Intellectual Property Organization (Site not responding. Last check: 2007-10-22)
		Applications that can potentially benefit from proteorhodopsin-light driven energy generation are, for instance, bio-electronics applications that are aimed to interface, integrate, or substitute the silicon based microelectronics systems as well as molecular devices.
		Other applications that can potentially benefit from proteorhodopsin-light driven energy generation are, for instance, in bio-materials, wherein proteorhodopsin is integrated as a bio-material in, for instance, optical films for light mediated computer memory applications, optical information storage and pattern recognition.
		The ability of proteorhodopsin to generate a physiologically significant membrane potential, even when heterologously expressed in nonnative membranes, is consistent with the proton pumping function for proteorhodopsin in the native gamma proteobacteria from which it is derived.
	www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=01/83701.011108&ELEMENT_SET=DECL (8595 words)

	Lecture 2 Notes
		conserved as potential energy in the form of ATP, it must be given off as heat.
		The chemiosmotic theory begins by describing the mechanism of coupling between substrate oxidation and phosphorylation.
		The chemiosmotic theory was presented as an hypothesis far in advance of experimental
	web.pdx.edu /~garlid/Lecture2-Notes.html (1151 words)

	Chemiosmotic Energy Conservation with Na+ as the Coupling Ion during Hydrogen-Dependent Caffeate Reduction by ...
		Chemiosmotic Energy Conservation with Na+ as the Coupling Ion during Hydrogen-Dependent Caffeate Reduction by Acetobacterium woodii -- Imkamp and Müller 184 (7): 1947 -- The Journal of Bacteriology
		Chemiosmotic Energy Conservation with Na as the Coupling Ion during Hydrogen-Dependent Caffeate Reduction by Acetobacterium woodii
		Ljungdahl, L. The acetyl-CoA pathway and the chemiosmotic generation of ATP during acetogenesis, p.
	jb.asm.org /cgi/content/full/184/7/1947 (2677 words)

	Chapter Abstracts: Strict and Facultative Anaerobes: Medical and Environmental Aspects
		Anaerobic respiratory chains use redox loops, redox-driven pumps, and the separation of proton-consuming and proton-producing reactions across the membrane to generate a chemiosmotic potential.
		Some anaerobes can generate a chemiosmotic potential by the electrogenic efflux of compounds across the membrane.
		Biostimulation of dehalogenating bacteria present in contaminated anaerobic habitats can be a potentially useful approach to enhance natural attenuation processes and is discussed with respect to the versatility of Dehalococcoides species.
	www.horizonpress.com /hsp/abs/absanaer.html (3751 words)

	MCB 229 Spring 2000: Catabolism: aerobic & anaerobic respiration
		Alternative solution is to use some non-organic molecule that has a low redox potential, can accept electrons and become some reduced molecule.
		Oxygen is perfect for this, has extremely low redox potential, and becomes reduced to water, the "perfect" waste product for an aqueous environment.
		Redox potential is + 0.42 v (compared to + 0.82 v for oxygen).
	dwb.unl.edu /Teacher/NSF/C11/C11Links/www.sp.uconn.edu/~terry/229sp00/lectures/catabolism2.html (1313 words)

	2 (Site not responding. Last check: 2007-10-22)
		One molecule of glucose stores more potential energy than one molecule of pyruvate because in glycolysis, some potential energy of the original glucose molecule is shared between 2 NADH and 2 ATP molecules.
		Substrate-level phosphorylation generates ATP directly from an enzyme-catalyzed reaction, whereas oxidative phosphorylation generates ATP indirectly by the chemiosmotic potential created by oxidative phosphorylation.
		C02 cannot serve as a source of free energy because the carbon atoms are fully oxidized; there are no H atoms bonded to any of the C valence electron positions.
	www2.kpr.edu.on.ca /cdciw/science/12biology/metabolism/metabolismhomework/respiration.htm (1638 words)

	Mitochondrial Transport of Cations: Channels, Exchangers, and Permeability Transition -- Bernardi 79 (4): 1127 -- ...
		It will now be useful to summarise the basis of the chemiosmotic coupling hypothesis in the form of four essential postulates;
		The 1960s and early 1970s witnessed a heated debate over chemiosmotic energy coupling (226), which was largely centered over
		In summary, the chemiosmotic hypothesis of energy conservation demands both the existence of electroneutral H
	physrev.physiology.org /cgi/content/full/79/4/1127 (8607 words)

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