Electron transfer pathway: Difference between revisions
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{{MitoPedia | {{MitoPedia | ||
|abbr= | |abbr=ET pathway | ||
|description= | |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]] | Β» [[#Electron transfer pathway versus electron transport chain |'''MiPNet article''']] | ||
|info=[[Gnaiger 2009 Int J Biochem Cell Biol]], [[Gnaiger 2020 BEC MitoPathways]] | |||
}} | }} | ||
__TOC__ | __TOC__ | ||
= Electron transfer pathway versus electron transport chain = | |||
{{Publication | {{Publication | ||
|title=Gnaiger E ( | |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= | |authors=Oroboros | ||
|year= | |year=2020 | ||
|journal= | |journal=MiPNet | ||
|abstract= | |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 | ||
}} | }} | ||
[[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 βETCβ 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). | ||
| | Β | ||
:::: 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 Β»[[Electron transfer pathway state]]). | |||
The term | ::::: (b) The term βchainβ 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 and electron transport are used synonymously. A general distinction, however, is helpful: | |||
( | :::: (i) '''Transfer''' (inter- or intramolecular) of a reactant involves a chemical reaction. Β | ||
:::: (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]]). | |||
== Electron transfer | == Related MitoPedia pages == | ||
::* '''Electron transfer pathway, ET pathway''' | |||
::::Β» [[Electron transfer pathway]] | |||
::::Β» [[Q-junction]] | |||
Electron transfer | ::* '''ET-pathway states''' | ||
::::Β» [[Electron-transfer-pathway state|ET-pathway state]] | |||
::* '''Coupling-control state ''E''''' | |||
::::[[File:E.jpg |link=ET capacity]] [[ET capacity]] | |||
::::Β» [[Noncoupled respiration]] | |||
::::Β» [[Uncoupler#Is_respiration_uncoupled_-_noncoupled_-_dyscoupled.3F |Is respiration uncoupled - noncoupled - dyscoupled?]] | |||
== References == | |||
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== | {{Keywords: Uncoupling}} | ||
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{{MitoPedia concepts | |||
|mitopedia concept=MiP concept | |||
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{{MitoPedia methods | |||
|mitopedia method=Respirometry | |||
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{{MitoPedia O2k and high-resolution respirometry}} | |||
{{MitoPedia topics | |||
|mitopedia topic=Enzyme, EAGLE | |||
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Latest revision as of 01:06, 31 December 2020
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. Β» MiPNet article
Abbreviation: ET pathway
Reference: Gnaiger 2009 Int J Biochem Cell Biol, Gnaiger 2020 BEC MitoPathways
Electron transfer pathway versus electron transport chain
Gnaiger E (2017) Electron transfer pathway versus electron transport chain. Mitochondr Physiol Network (2010-08-17) last update 2020-06-02. |
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.
β’ O2k-Network Lab: AT Innsbruck Gnaiger E
- 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 βETCβ 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 Β»Electron transfer pathway state).
- (b) The term βchainβ 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
- ET-pathway states
- Coupling-control state E
References
Bioblast link | Reference | Year |
---|---|---|
Gnaiger 2009 Int J Biochem Cell Biol | Gnaiger E (2009) Capacity of oxidative phosphorylation in human skeletal muscle. New perspectives of mitochondrial physiology. Int J Biochem Cell Biol 41:1837-45. https://doi.org/10.1016/j.biocel.2009.03.013 | 2009 |
Gnaiger 2020 BEC MitoPathways | 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:2020-0002 | 2020 |
BEC 2020.1 doi10.26124bec2020-0001.v1 | Gnaiger E et al β MitoEAGLE Task Group (2020) Mitochondrial physiology. Bioenerg Commun 2020.1. https://doi.org/10.26124/bec:2020-0001.v1 | 2020 |
Hatefi 1962 J Biol Chem-XLII | 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)73804-6 | 1962 |
- Bioblast links: Uncoupling - >>>>>>> - Click on [Expand] or [Collapse] - >>>>>>>
- Specific
- Β» Artefacts by single dose uncoupling
- Β» ATP synthase
- Β» CCCP
- Β» Coupling-control protocol
- Β» DNP
- Β» Dyscoupled respiration
- Β» FCCP
- Β» Is respiration uncoupled - noncoupled - dyscoupled?
- Β» Noncoupled respiration: Discussion
- Β» Uncoupler
- Β» Uncoupled respiration - see Β» Noncoupled respiration
- Β» Uncoupling proteins
- Β» Uncoupling protein 1
- Β» Uncoupler titrations - Optimum uncoupler concentration
- Specific
- Respiratory states and control ratios
- Β» Biochemical coupling efficiency
- Β» Coupling-control state
- Β» Electron-transfer-pathway state
- Β» Electron-transfer pathway
- ET capacity
- Β» E-L coupling efficiency
- Β» Flux control efficiency
- Β» Flux control ratio
- Β» LEAK-control ratio
- Β» LEAK respiration
- Β» Noncoupled respiration
- Β» OXPHOS
- Β» OXPHOS capacity; Β» State 3
- Β» OXPHOS-control ratio, P/E ratio
- Β» Respiratory acceptor control ratio
- Β» ROUTINE-control ratio
- Β» ROUTINE respiration
- Β» ROUTINE state
- Β» State 3u
- Β» State 4
- Β» Uncoupling-control ratio UCR
- Respiratory states and control ratios
- Gnaiger E et al β MitoEAGLE Task Group (2020) Mitochondrial physiology. Bioenerg Commun 2020.1. https://doi.org/10.26124/bec:2020-0001.v1
- 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:2020-0002
- General (alphabetical order)
- Other keyword lists
MitoPedia concepts:
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MitoPedia methods:
Respirometry
MitoPedia topics: Enzyme, EAGLE
Labels:
HRR: Theory