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Difference between revisions of "Electron transfer pathway"

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{{MitoPedia
{{MitoPedia
|abbr=ETS
|abbr=ET pathway
|description=[[File:E.jpg |link=ETS capacity]] The mitochondrial '''electron transfer system''' (ETS; synonymous with 'electron transport system') transfers electrons from externally supplied reduced substrates to oxygen. It consists of the [[membrane-bound ETS|membrane-bound ETS (mETS)]] with enzyme complexes located in the inner [[mt-membrane]], mt-matrix dehydrogenases generating NADH, and the transport systems involved in metabolite exchange across the mt-membranes (see [[ETS capacity]]). [[Electron_transfer_system#Electron_transfer_system_versus_electron_transport_chain |» '''MiPNet article''']]
|description=In the mitochondrial '''electron transfer pathway''' (ET pathway) electrons are transferred from externally supplied reduced fuel substrates to oxygen. Based on this experimentally oriented definition (see [[ET capacity]]), the ET pathway consists of (1) the [[membrane-bound ET pathway]] with respiratory complexes located in the inner mt-membrane, (2) [[TCA cycle]] and other mt-matrix dehydrogenases generating NADH and succinate, and (3) the carriers involved in metabolite transport across the mt-membranes.
|info=[[Gnaiger 2009 Int J Biochem Cell Biol]]
» [[#Electron transfer pathway versus electron transport chain |'''MiPNet article''']]
|type=Respiration
|info=[[Gnaiger 2009 Int J Biochem Cell Biol]], [[Gnaiger 2014 MitoPathways]]
}}
{{MitoPedia methods
|mitopedia method=Respirometry
|type=Respiration
}}
{{MitoPedia topics
|mitopedia topic=Respiratory state
|type=Respiration
}}
}}
__TOC__
__TOC__
= Electron transfer system versus electron transport chain =
= Electron transfer pathway versus electron transport chain =
{{Publication
{{Publication
|title=Gnaiger E (2013) Electron transfer system versus electron transport chain. Mitochondr Physiol Network 2013-08-18.
|title=Gnaiger E (2017) Electron transfer pathway versus electron transport chain. Mitochondr Physiol Network (2010-08-17) last update 2020-06-02.
|info=[[Gnaiger 2012 MitoPathways]]
|info=
|authors=OROBOROS
|authors=Oroboros
|year=2013
|year=2020
|journal=MiPNet
|journal=MiPNet
|abstract=The well established terms 'respiratory chain' or 'electron transfer chain' suggest erroneously that the convergent '''electron transfer system''' may be designed as a simple ''chain''.
|abstract=Conventionally, the 'electron transport chain' has been considered as the sequence of membrane-bound respiratory complexes, mainly CI and CII feeding electrons into the [[Q-junction]], and CIII and CIV linked by cytochrome ''c''. Emphasis on the term '''electron transfer pathway''' ([[Gnaiger 2020 MitoPathways]]) clarifies (''1'') the convergent structure of the mitochondrial pathways, (''2'') the upstream modules of electron transfer from externally supplied fuel substrates, transport into the matrix space, and matrix dehydrogenases, including the [[TCA cycle]] and the [[N-junction]].
|mipnetlab=AT Innsbruck Gnaiger E
|mipnetlab=AT Innsbruck Gnaiger E
}}
}}
{{Labeling
[[File:Hatefi 1962 NS 2012.jpg|right|500px|Q-junction]]
|couplingstates=ETS
:::: The well established terms 'respiratory chain' or 'electron transfer chain' suggest erroneously that the convergent '''electron transfer pathway''' may be designed as a simple ''chain''. But the term '''electron transport chain''' (or electron transfer chain, ETC) is a misnomer. Understanding mitochondrial respiratory control has suffered greatly from this inappropriate terminology, although textbooks using the term ETC (Lehninger 1970) make it sufficiently clear that '''electron transfer is not arranged as a chain''': the „ETC‟ is in fact not a simple chain but an arrangement of electron transfer complexes in a non-linear, convergent electron transfer pathway. The classically introduced term '''Electron transfer pathway''' ([[Hatefi 1962 J Biol Chem-XLII |Hatefi et al 1962]]) is more accurate. Since the enzyme-catalyzed steps form a metabolic pathway, the term '''electron transfer pathway''' is accurate and sufficient (IUB 1991).
|instruments=Theory
}}
== Electron transfer system versus chain ==
 
The term '''electron transport chain''' (or electron transfer chain, ETC) is a misnomer. Understanding mitochondrial respiratory control has suffered greatly from this inappropriate terminology, although textbooks using the term ETC (Lehninger 1970) make it sufficiently clear that '''electron transfer systems are not arranged as a chain''': the „ETC‟ is in fact not a simple chain but an arrangement of electron transfer complexes in a non-linear, convergent electron transfer system. The classically introduced term '''electron transfer system''' (Hatefi et al 1962 <ref> Hatefi Y, Haavik AG, Fowler LR, Griffiths DE (1962) Studies on the '''electron transfer system''' XLII. Reconstitution of the electron transfer system. J Biol Chem 237: 2661-2669. [[Hatefi 1962 J Biol Chem-XLII |»Open Access]]</ref>) is accurate and sufficient. <ref> International Union of Biochemistry (1991) Nomenclature of '''electron-transfer proteins.''' Biochim Biophys Acta 1060. [http://www.chem.qmul.ac.uk/iubmb/etp/ »Open Access]</ref>
 
The established convention of defining the 'electron transport chain' as being comprised of four Complexes has conceptual weaknesses.  


(a) In fact, there are at least six Complexes of mitochondrial electron transfer: In addition to Complexes I and II, [[Glycerophosphate_dehydrogenase|glycerophosphate dehydrogenase]] (GpDH) and [[Electron-transferring_flavoprotein|electron transferring flavoprotein]] (ETF) are involved in the [[Q-junction]] with electron transfer to [[Complex III]].
:::: The established convention of defining the 'electron transport chain' as being comprised of four Complexes has conceptual weaknesses.  
<ref>International Union of Biochemistry (1991) Nomenclature of '''electron-transfer proteins.''' Biochim Biophys Acta 1060. [http://www.chem.qmul.ac.uk/iubmb/etp/ »Open Access]</ref>,<ref>Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. [[Gnaiger_2012_MitoPathways |»Open Access]]</ref>


(b) The term „chain‟ suggests a linear sequence, whereas the functional structure of the electron transfer system can only be understood by recognizing '''the convergence of electron flow at the Q-junction''', followed by a chain of Complexes III and IV, mediated by [[cytochrome c | cytochrome ''c'']]. <ref> Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. [[Gnaiger_2012_MitoPathways |»Open Access]]</ref>
::::: (a) In fact, there are more than six Complexes of mitochondrial electron transfer (not including [[Complex V]], which is not part of the ET pathway): CI to CIV, and additional respiratory complexes linked to pathways converging at the [[Q-junction]] (see »[[Electron transfer pathway state]]).


Electrons flow to oxygen from either [[Complex I]] with a total of three coupling sites, or from [[Complex II]] and other flavoproteins, providing multiple entries into the Q-cycle with two coupling sites downstream. <ref> Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. [[Gnaiger_2012_MitoPathways |»Open Access]]</ref>
::::: (b) The term „chain‟ suggests a linear sequence, whereas the functional structure of the electron transfer pathway can only be understood by recognizing '''the convergence of electron flow at the Q-junction''', followed by a chain of Complexes III and IV, mediated by [[cytochrome c | cytochrome ''c'']] (Gnaiger 2014). Electrons flow to oxygen from either [[Complex I]] with a total of three coupling sites, or from [[Complex II]] and other flavoproteins, providing multiple entries into the Q-junction with two coupling sites downstream (Gnaiger 2014).




== Electron transfer versus transport ==
== Electron transfer versus transport ==
:::: Electron transfer and electron transport are used synonymously. A general distinction, however, is helpful:


Electron transfer and electron transport are used synonymously. A general distinction, however, may be helpful:
:::: (i) '''Transfer''' (inter- or intramolecular) of a reactant involves a chemical reaction.  


(i) '''Transfer''' (inter- or intramolecular) of a reactant involves a chemical reaction.  
:::: (ii) '''Transport''' (from one location to another) of an entity is a (vectorial) process in contrast to a chemical reaction ([[Cohen 2008 IUPAC Green Book |IUPAC Green Book]]).


(ii) '''Transport''' (from one place to another) of an entity is a (vectorial) process in contrast to a chemical reaction.
<ref> International Union of Biochemistry and Molecular Biology. Recommendations for terminology and databases for biochemical thermodynamics - The IUPAC Green Book [http://www.chem.qmul.ac.uk/iubmb/thermod2/ »Open Access].</ref>


== Related MitoPedia pages ==
::* '''Electron transfer pathway, ET pathway'''
::::» [[Electron transfer pathway]]
::::» [[Q-junction]]


== Related terms in Bioblast ==
::* '''ET-pathway states'''
[[File:ETS.png|300px|thumb|Noncoupled respiration with a shortcircuit of the proton cycle across the inner mt-membrane at optimum uncoupler (protonophore) concentration stimulating maximum oxygen flux. 2[H] indicates the reduced hydrogen equivalents of CHO substrates and electron transfer to oxygen. H<sup>+</sup><sub>out</sub> are protons pumped out of the matrix phase. Proton leaks dissipate energy of translocated protons. ETS capacity is not limited by the capacity of the phosphorylation system (uncontrolled state; modified after [[Gnaiger 2012 MitoPathways]]).]]
::::» [[Electron-transfer-pathway state|ET-pathway state]]
[[File:P.jpg |link=OXPHOS capacity]] [[OXPHOS capacity |OXPHOS]], ''P''


[[File:E.jpg |link=ETS capacity]] [[ETS capacity |ETS]], ''E''
::* '''Coupling-control state ''E'''''
::::[[File:E.jpg |link=ET capacity]] [[ET capacity]]
::::» [[Noncoupled respiration]]
::::» [[Uncoupler#Is_respiration_uncoupled_-_noncoupled_-_dyscoupled.3F |Is respiration uncoupled - noncoupled - dyscoupled?]]


[[File:R.jpg |link=ROUTINE respiration]] [[ROUTINE respiration |ROUTINE]], ''R''
== References ==


[[File:L.jpg |link=LEAK respiration]] [[LEAK respiration |LEAK]], ''L''
{{#ask:[[Additional label::Electron transfer pathway]]
| mainlabel=Bioblast link
|?Has title=Reference
|?Was published in year=Year
|format=broadtable
|limit=5000
|offset=0
|sort=Has title
|order=ascending
}}


[[File:ROX.jpg |link=Residual oxygen consumption]] [[Residual oxygen consumption |ROX]], ''R''
{{Keywords: Uncoupling}}


=== The ETS state ===
{{MitoPedia concepts
* [[ETS capacity]] - [[State 3u]]<ref>Gnaiger E. Why not State 3u? Mitochondr Physiol Network. »[[ETS capacity]]</ref>
|mitopedia concept=MiP concept
* [[ETS-competent substrate state]]
}}
* [[Level flow]]
{{MitoPedia methods
* [[Noncoupled respiration]] - [[Uncoupler]]<ref>Gnaiger E. Is respiration uncoupled - noncoupled - dyscoupled? Mitochondr Physiol Network. »[[Uncoupler]]</ref>
|mitopedia method=Respirometry
* [[Phosphorylation control protocol]]
}}
{{MitoPedia O2k and high-resolution respirometry}}
{{MitoPedia topics
|mitopedia topic=Enzyme, EAGLE
}}


=== ETS-related flux control factors ===
{{Labeling
* [[Biochemical coupling efficiency]]<ref>Gnaiger E. Biochemical coupling efficiency: from 0 to <1. Mitochondr Physiol Network. »[[Biochemical coupling efficiency]]</ref>
|instruments=Theory
* [[E-L coupling control factor]] - [[E-P coupling control factor]] - [[E-R coupling control factor]]
}}
 
=== ETS-related flux control ratios ===
* [[Coupling control ratio]] - [[Uncoupling control ratio]]
* [[LEAK control ratio per E]] - [[Phosphorylation system control ratio]]
* [[ROUTINE control ratio]] - [[NetROUTINE control ratio]]
 
 
== References ==
<references/>

Revision as of 14:25, 8 June 2020


high-resolution terminology - matching measurements at high-resolution


Electron transfer pathway

Description

In the mitochondrial electron transfer pathway (ET pathway) electrons are transferred from externally supplied reduced fuel substrates to oxygen. Based on this experimentally oriented definition (see ET capacity), the ET pathway consists of (1) the membrane-bound ET pathway with respiratory complexes located in the inner mt-membrane, (2) TCA cycle and other mt-matrix dehydrogenases generating NADH and succinate, and (3) the carriers involved in metabolite transport across the mt-membranes. » MiPNet article

Abbreviation: ET pathway

Reference: Gnaiger 2009 Int J Biochem Cell Biol, Gnaiger 2014 MitoPathways

Electron transfer pathway versus electron transport chain

Publications in the MiPMap
Gnaiger E (2017) Electron transfer pathway versus electron transport chain. Mitochondr Physiol Network (2010-08-17) last update 2020-06-02.


Oroboros (2020) MiPNet

Abstract: Conventionally, the 'electron transport chain' has been considered as the sequence of membrane-bound respiratory complexes, mainly CI and CII feeding electrons into the Q-junction, and CIII and CIV linked by cytochrome c. Emphasis on the term electron transfer pathway (Gnaiger 2020 MitoPathways) clarifies (1) the convergent structure of the mitochondrial pathways, (2) the upstream modules of electron transfer from externally supplied fuel substrates, transport into the matrix space, and matrix dehydrogenases, including the TCA cycle and the N-junction.


O2k-Network Lab: AT Innsbruck Gnaiger E

Q-junction
The well established terms 'respiratory chain' or 'electron transfer chain' suggest erroneously that the convergent electron transfer pathway may be designed as a simple chain. But the term electron transport chain (or electron transfer chain, ETC) is a misnomer. Understanding mitochondrial respiratory control has suffered greatly from this inappropriate terminology, although textbooks using the term ETC (Lehninger 1970) make it sufficiently clear that electron transfer is not arranged as a chain: the „ETC‟ is in fact not a simple chain but an arrangement of electron transfer complexes in a non-linear, convergent electron transfer pathway. The classically introduced term Electron transfer pathway (Hatefi et al 1962) is more accurate. Since the enzyme-catalyzed steps form a metabolic pathway, the term electron transfer pathway is accurate and sufficient (IUB 1991).
The established convention of defining the 'electron transport chain' as being comprised of four Complexes has conceptual weaknesses.
(a) In fact, there are more than six Complexes of mitochondrial electron transfer (not including Complex V, which is not part of the ET pathway): CI to CIV, and additional respiratory complexes linked to pathways converging at the Q-junction (see »Electron transfer pathway state).
(b) The term „chain‟ suggests a linear sequence, whereas the functional structure of the electron transfer pathway can only be understood by recognizing the convergence of electron flow at the Q-junction, followed by a chain of Complexes III and IV, mediated by cytochrome c (Gnaiger 2014). Electrons flow to oxygen from either Complex I with a total of three coupling sites, or from Complex II and other flavoproteins, providing multiple entries into the Q-junction with two coupling sites downstream (Gnaiger 2014).


Electron transfer versus transport

Electron transfer and electron transport are used synonymously. A general distinction, however, is helpful:
(i) Transfer (inter- or intramolecular) of a reactant involves a chemical reaction.
(ii) Transport (from one location to another) of an entity is a (vectorial) process in contrast to a chemical reaction (IUPAC Green Book).


Related MitoPedia pages

  • Electron transfer pathway, ET pathway
» Electron transfer pathway
» Q-junction
  • ET-pathway states
» ET-pathway state
  • Coupling-control state E
E.jpg ET capacity
» Noncoupled respiration
» Is respiration uncoupled - noncoupled - dyscoupled?

References

Bioblast linkReferenceYear
Gnaiger E (2009) Capacity of oxidative phosphorylation in human skeletal muscle. New perspectives of mitochondrial physiology. https://doi.org/10.1016/j.biocel.2009.03.0132009
Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Bioenerg Commun 2020.2. https://doi.org/10.26124/bec:2020-00022020
Gnaiger E et al ― MitoEAGLE Task Group (2020) Mitochondrial physiology. Bioenerg Commun 2020.1. https://doi.org/10.26124/bec:2020-0001.v12020
Hatefi Y, Haavik AG, Fowler LR, Griffiths DE (1962) Studies on the electron transfer system XLII. Reconstitution of the electron transfer system. J Biol Chem 237:2661-9. https://doi.org/10.1016/S0021-9258(19)73804-61962


Questions.jpg


Click to expand or collaps
Bioblast links: Uncoupling - >>>>>>> - Click on [Expand] or [Collapse] - >>>>>>>
Specific
» Artefacts by single dose uncoupling
» ATP synthase
» CCCP
» Coupling-control protocol
» DNP
» Dyscoupled respiration
» FCCP
» Is respiration uncoupled - noncoupled - dyscoupled?
» Noncoupled respiration: Discussion
» Uncoupler
» Uncoupled respiration - see » Noncoupled respiration
» Uncoupling proteins
» Uncoupling protein 1
» Uncoupler titrations - Optimum uncoupler concentration
Respiratory states and control ratios
» Biochemical coupling efficiency
» Coupling-control state
» Electron-transfer-pathway state
» Electron-transfer pathway
E.jpg ET capacity
» E-L coupling efficiency
» Flux control efficiency
» Flux control ratio
» LEAK-control ratio
» LEAK respiration
» Noncoupled respiration
» OXPHOS
» OXPHOS capacity; » State 3
» OXPHOS-control ratio, P/E ratio
» Respiratory acceptor control ratio
» ROUTINE-control ratio
» ROUTINE respiration
» ROUTINE state
» State 3u
» State 4
» Uncoupling-control ratio UCR
General (alphabetical order)
» Adenine nucleotide translocase
» Adenylates
» Electron transfer pathway
» Mitochondrial preparations
» mt-membrane potential
» Oxygen flux
» Phosphorylation system
» Proton leak
» Proton slip
» TIP2k
Other keyword lists
» Template:Keywords: Force and membrane potential



MitoPedia concepts: MiP concept 


MitoPedia methods: Respirometry 



MitoPedia topics: Enzyme, EAGLE 


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