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Difference between revisions of "Electron transfer pathway"

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{{MitoPedia
{{MitoPedia
|abbr=ET-pathway
|abbr=ET pathway
|description=In the mitochondrial '''electron transfer-pathway''' (ET-pathway) electrons are transfered 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.
|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.
» [[#Electron transfer pathway versus electron transport chain |'''MiPNet article''']]
» [[#Electron transfer pathway versus electron transport chain |'''MiPNet article''']]
|info=[[Gnaiger 2009 Int J Biochem Cell Biol]], [[Gnaiger 2014 MitoPathways]]
|info=[[Gnaiger 2009 Int J Biochem Cell Biol]], [[Gnaiger 2020 BEC MitoPathways]]
}}
{{MitoPedia concepts
|mitopedia concept=MiP concept
}}
{{MitoPedia methods
|mitopedia method=Respirometry
}}
{{MitoPedia O2k and high-resolution respirometry}}
{{MitoPedia topics
|mitopedia topic=Enzyme, EAGLE
}}
}}
__TOC__
__TOC__
= Electron transfer pathway versus electron transport chain =
= Electron transfer pathway versus electron transport chain =
{{Publication
{{Publication
|title=Gnaiger E (2017) Electron transfer pathway versus electron transport chain. Mitochondr Physiol Network 2010-08-17, edited 2014-07-06, 2017-02-17, 2017-10-10.
|title=Gnaiger E (2017) Electron transfer pathway versus electron transport chain. Mitochondr Physiol Network (2010-08-17) last update 2020-06-02.
|info=
|info=
|authors=OROBOROS
|authors=Oroboros
|year=2017
|year=2020
|journal=MiPNet
|journal=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''' (or Electron transfer-pathway, [[Gnaiger 2014 MitoPathways]]) clarifies (i) the convergent structure of the mitochondrial pathways, (ii) 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]].
|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 BEC 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
|instruments=Theory
}}
}}
[[File:Hatefi 1962 NS 2012.jpg|right|500px|Q-junction]]
[[File:Hatefi 1962 NS 2012.jpg|right|500px|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 1962 J Biol Chem-XLI |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 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).


:::: The established convention of defining the 'electron transport chain' as being comprised of four Complexes has conceptual weaknesses.  
:::: 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]]).
::::: (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 | 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).
::::: (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).
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== Related MitoPedia pages ==
== Related MitoPedia pages ==
::* '''Electron transfer pathway, ET pathway'''
::* '''Electron transfer pathway, ET pathway'''
::::» [[Electron transfer-pathway]]
::::» [[Electron transfer pathway]]
::::» [[Q-junction]]
::::» [[Q-junction]]


::* '''ET-pathway states'''
::* '''ET-pathway states'''
::::» [[Electron transfer-pathway state|ET-pathway state]]
::::» [[Electron-transfer-pathway state|ET-pathway state]]


::* '''Coupling control state ''E'''''
::* '''Coupling-control state ''E'''''
::::[[File:E.jpg |link=ET-capacity]] [[ET-capacity]]
::::[[File:E.jpg |link=ET capacity]] [[ET capacity]]
::::» [[Noncoupled respiration]]
::::» [[Noncoupled respiration]]
::::» [[Uncoupler#Is_respiration_uncoupled_-_noncoupled_-_dyscoupled.3F |Is respiration uncoupled - noncoupled - dyscoupled?]]
::::» [[Uncoupler#Is_respiration_uncoupled_-_noncoupled_-_dyscoupled.3F |Is respiration uncoupled - noncoupled - dyscoupled?]]
== References ==
{{#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
}}
{{Keywords: Uncoupling}}
{{MitoPedia concepts
|mitopedia concept=MiP concept
}}
{{MitoPedia methods
|mitopedia method=Respirometry
}}
{{MitoPedia O2k and high-resolution respirometry}}
{{MitoPedia topics
|mitopedia topic=Enzyme, EAGLE
}}
{{Labeling
|instruments=Theory
}}

Latest revision as of 00:06, 31 December 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 2020 BEC 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 BEC 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


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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
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» Template:Keywords: Force and membrane potential



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