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	~~== Reverse Electron Flow ==~~

	~~[[File:~~Reverse Electron Flow ~~Diagram.png~~\|~~thumb~~\|~~Diagram illustrating the process of reverse electron flow]]~~		{{Short description\|Biochemical process in cellular respiration}}
			{{Infobox biochemical pathway
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	'''Reverse electron flow''' ~~(also known as '''reversed electron transport''' or '''RET''')~~ is a process in [[microbiology]] and [[biochemistry]] where electrons are moved against their electrochemical gradient across a [[biological membrane]]. This process is primarily observed in [[prokaryotic]] organisms, such as [[bacteria]] and [[archaea]], and is ~~a key component~~ of their [[~~metabolism]].~~		'''Reverse electron flow''' is a biochemical process that occurs in certain [[microorganisms]] and is part of their [[metabolic pathways]]. This process is essential for the generation of [[reducing power]] in the form of [[NADH]] or [[NADPH]], which are crucial for various [[biosynthetic reactions]].

	~~== Overview ==~~

	~~In normal [[electron transport chain]] (ETC), electrons move from a high energy state to a lower one, releasing energy that is used to pump protons across a membrane, creating a [[proton gradient~~]]. This ~~gradient~~ is ~~then used to generate [[adenosine triphosphate]] (ATP),~~ the ~~energy currency~~ of ~~the cell, through a process known as~~ [[~~oxidative phosphorylation~~]].

	In reverse electron flow, the process is essentially reversed. ATP is used to pump protons across the membrane, creating an electrochemical gradient that drives electrons to move from a low energy state to a higher one. This process is used by certain organisms to generate reducing power in the form of [[~~reduced nicotinamide adenine dinucleotide~~]] ~~(NADH)~~ or [[~~reduced nicotinamide adenine dinucleotide phosphate~~]] ~~(NADPH)~~.

	== Mechanism ==		== Mechanism ==
			In reverse electron flow, electrons are transferred from a donor with a lower [[reduction potential]] to an acceptor with a higher reduction potential, against the thermodynamic gradient. This process requires the input of energy, which is typically derived from the [[proton motive force]] generated by the [[electron transport chain]].

	[[~~File:Mechanism of Reverse Electron Flow~~.~~png\|thumb\|Mechanism of~~ reverse electron flow]]		The reverse electron flow is often observed in [[chemolithoautotrophs]], which are organisms that obtain energy by oxidizing inorganic substances. These organisms use reverse electron flow to generate NADH from NAD+ when the direct reduction of NAD+ is not thermodynamically favorable.

	~~The mechanism of reverse~~ electron flow ~~varies among different~~ organisms, ~~but generally involves the following steps:~~		== Biological Significance ==
			Reverse electron flow is significant in the [[carbon fixation]] pathways of certain bacteria, such as the [[Calvin cycle]] in [[cyanobacteria]] and some [[purple bacteria]]. It allows these organisms to assimilate carbon dioxide into organic compounds, which is vital for their growth and survival.

	~~# ATP~~ is ~~hydrolyzed to pump protons across~~ the ~~membrane~~, ~~creating a proton gradient.~~		== Examples ==
	~~# The proton gradient drives~~ the ~~movement~~ of ~~electrons from a low energy state to a higher one.~~		One example of reverse electron flow is found in the [[sulfur-oxidizing bacteria]], where electrons from the oxidation of sulfur compounds are used to reduce NAD+ to NADH. Another example is in the [[nitrifying bacteria]], which oxidize ammonia to nitrite and use reverse electron flow to generate reducing power for [[carbon assimilation]].
	~~# The high-energy electrons~~ are used to reduce NAD~~+ or NADP~~+ to NADH ~~or NADPH~~, ~~respectively~~.

	== ~~Significance~~ ==		== See also ==
			* [[Electron transport chain]]
			* [[Proton motive force]]
			* [[Chemolithoautotrophy]]
			* [[Carbon fixation]]

	~~Reverse electron flow is significant in several ways:~~		== References ==
			{{Reflist}}

	~~# It allows organisms to generate reducing power in the form of NADH or NADPH, which are essential for various metabolic processes, including [[anabolism]] and [[biosynthesis]].~~		== External links ==
	~~# It enables certain organisms to survive in environments with limited nutrients or energy sources.~~		* [https://www.wikimd.com/wiki/Reverse_electron_flow Reverse Electron Flow on WikiMD]
	~~# It provides a mechanism for the regulation of cellular metabolism and energy balance.~~

	== ~~See Also~~ ==

	* [[Electron ~~transport chain]]~~
	* [[Oxidative phosphorylation]]
	* [[Proton gradient]]
	* [[Adenosine triphosphate]]
	* [[Reduced nicotinamide adenine dinucleotide]]
	* [[Reduced nicotinamide adenine dinucleotide phosphate]]

			[[Category:Biochemistry]]
			[[Category:Metabolic pathways]]
	[[Category:Microbiology]]		[[Category:Microbiology]]
	~~[[Category:Biochemistry]]~~
	[[Category:Cellular respiration]]		[[Category:Cellular respiration]]
	~~[[Category:Metabolism]]~~

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== Reverse Electron Flow ==

[[File:Reverse Electron Flow Diagram.png|thumb|Diagram illustrating the process of reverse electron flow]]

'''Reverse electron flow''' (also known as '''reversed electron transport''' or '''RET''') is a process in [[microbiology]] and [[biochemistry]] where electrons are moved against their electrochemical gradient across a [[biological membrane]]. This process is primarily observed in [[prokaryotic]] organisms, such as [[bacteria]] and [[archaea]], and is a key component of their [[metabolism]].

== Overview ==

In normal [[electron transport chain]] (ETC), electrons move from a high energy state to a lower one, releasing energy that is used to pump protons across a membrane, creating a [[proton gradient]]. This gradient is then used to generate [[adenosine triphosphate]] (ATP), the energy currency of the cell, through a process known as [[oxidative phosphorylation]].

In reverse electron flow, the process is essentially reversed. ATP is used to pump protons across the membrane, creating an electrochemical gradient that drives electrons to move from a low energy state to a higher one. This process is used by certain organisms to generate reducing power in the form of [[reduced nicotinamide adenine dinucleotide]] (NADH) or [[reduced nicotinamide adenine dinucleotide phosphate]] (NADPH).

== Mechanism ==

[[File:Mechanism of Reverse Electron Flow.png|thumb|Mechanism of reverse electron flow]]

The mechanism of reverse electron flow varies among different organisms, but generally involves the following steps:

# ATP is hydrolyzed to pump protons across the membrane, creating a proton gradient.
# The proton gradient drives the movement of electrons from a low energy state to a higher one.
# The high-energy electrons are used to reduce NAD+ or NADP+ to NADH or NADPH, respectively.

== Significance ==

Reverse electron flow is significant in several ways:

# It allows organisms to generate reducing power in the form of NADH or NADPH, which are essential for various metabolic processes, including [[anabolism]] and [[biosynthesis]].
# It enables certain organisms to survive in environments with limited nutrients or energy sources.
# It provides a mechanism for the regulation of cellular metabolism and energy balance.

== See Also ==

* [[Electron transport chain]]
* [[Oxidative phosphorylation]]
* [[Proton gradient]]
* [[Adenosine triphosphate]]
* [[Reduced nicotinamide adenine dinucleotide]]
* [[Reduced nicotinamide adenine dinucleotide phosphate]]

[[Category:Microbiology]]
[[Category:Biochemistry]]
[[Category:Cellular respiration]]
[[Category:Metabolism]]

Reverse electron flow - Revision history

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