Talk:Anaerobic respiration

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This article is a disaster, extremely poorly written, mostly incomprehensible and full of mistakes, I shudder to think of students around the world coming here for information ... —Preceding unsigned comment added by (talk) 02:51, 28 May 2010 (UTC)

"Lactic acid" fermentation[edit]

The equations for anaerobic respiration using lactic acid fermentation are always given as
C6H12O6 --> 2 C3H6O3
and this lactic acid production causes acidosis (resulting in muscle fatigue)
but it is actually
C6H12O6 --> 2 CH3CH3COO- + 2H+
CH3CH3COO- is always produced in salt form and the net H+ production is due to a greater rate of ATP hydrolysis than can be matched by oxidative phosphorylation, meaning that acidosis is not caused by "lactic acid" fermentation. On the contrary, lactate acts in one of the membrane exchange systems for cell proton buffering -- sarcolemmal transport of protons out of the cytosol through lactate/H+ symporters.
The reference I found is It seems to me that the current textbooks have maintained the possible misconception of acidosis due to lactic acid as well. Can an expert clarify this? I just found the perhaps more accurate account given in the article on lactic acid
Lim Wei Quan 10:55, 24 May 2007 (UTC)

Merge with fermentation (biochemistry)[edit]

I propose a merge with, and migration from, fermentation (biochemistry). The biochemistry of fermentation is anaerobic respiration of sugars to ethanol. Zephyris Talk 13:57, 4 November 2006 (UTC)

  • This would be absoultely insane, the two processes are approaced totally differently in biology. This proposal is more suited to the title of an essay for undergraduates than a serious encyclopedia.
as far as i know, fermentation has been a topic for year 2 Higher diploma which major in biotechnology in Hong Kong already. back to the matter, i don't agree with the merge since they are totally different in both meaning and process. meaningless 16:49, 12 December 2006 (UTC)
In an attempt to clean the article up a little bit, I added a new heading, "Anaerobic fermentation in prokaryotes," which includes a very brief explanation of the difference between the two processes. I don't feel quite bold enough to delete the fermentation sections since there are so many people out there that use the two terms interchangeably. There are many web sites, including several wikipedia articles, that confuse the two processes. NighthawkJ 17:46, 28 November 2006 (UTC)
  • I vote a definite no on the proposal to merge. The terms "anaerobic respiration" and "fermentation" are not interchangeable. The breakdown of glucose to lactic acid described in the current version of the article is an example of fermentation, not anaerobic respiration. Anaerobic respiration, like aerobic respiration, involves an electron transport chain, with the terminal electron acceptor being something other than oxygen. The electron transport chain is not involved in the fermentation of glucose to lactic acid or ethanol. Therefore, descriptions of lactic acid and ethanol fermentation need to be removed from this article and replaced with examples of anaerobic respiration. NighthawkJ 05:49, 17 November 2006 (UTC)
This is true, but anaerobic respiration, which is defined as "the oxidation of molecules in the absence of oxygen to produce energy" includes fermentation as a specific example of non-electron chain anaerobic respiration.—The preceding unsigned comment was added by Zephyris (talkcontribs) 08:21, 17 November 2006.
Actually, the definition isn't quite correct. Anaerobic respiration is defined as "the oxidation of molecules in the presence of an external electron acceptor (other than oxygen) to produce energy." The use of an external electron acceptor requires an electron transport chain. Fermentation clearly does not fit this definition since it does not involve an external electron acceptor. In fermentation, a molecule derived from the partial oxidation of glucose, pyruvate, is used as an internal electron acceptor. This is an important distinction because the partial oxidation of glucose in fermentation does not permit the synthesis of as much ATP as observed with the complete oxidation of glucose observed with anaerobic respiration. Complete glucose oxidation is possible in anaerobic respiration because of the use of an external electron acceptor via an electron transport chain. I'm open to the possibility that other fields use the definition currently stated in the article, but the bacterial physiology textbooks that I've seen all make a distinction between fermentation and anaerobic respiration. NighthawkJ 04:44, 18 November 2006 (UTC)
That point had eluded me. -- Paleorthid 15:59, 18 November 2006 (UTC)

Fully agree with Nighthawk - and want to actuallt further clarify that fermentation may involve intermediate reactions that involve oxidation and reduction, but there is not NET oxidation in fermentation - i.e. whaever molecule (such as glucose) you start with, neither gains nor loses electrons if you compare it to the FINAL products of the fermentation reaction - and this is exactly because there is no EXTERNAL terminal electron acceptor. - DocMelvis (talk) 06:58, 26 April 2008 (UTC)

  • I support(support withdrawn per above -- 15:59, 18 November 2006 (UTC)) the proposal to merge, but with some misgivings about my POV. Certainly fermentation is more commonly viewed as related to fermentation (food) or industrial fermentation, I have no misgivings about that. But fermentation has many subtle biochemical nuances that are fascinating in their own right: is a discussion in the offing for fermentation-related products like aldehyde, alkene, ester, ketone, and epoxide? Will it fit into anaerobic respiration? into fermentation? I simply don't have a good idea. My support(support withdrawn per above -- 15:59, 18 November 2006 (UTC)) for merge is based on what I know. In biogeochemistry applications (wetland chemistry, bioremediation) and in waste treatment, fermentation is not a term commonly used, despite indications to the contrary in industrial fermentation. This is because fermentation is only one of the anoxic and anaerobic processes that occur in sequence, one minor sub-step down the biogeochemical redox ladder, with carbon dioxide and water generation at the top and hydrogen generation at the bottom. See this PPT. Thus covering fermentation in anaerobic respiration is fine from my perspective. -- Paleorthid 17:50, 17 November 2006 (UTC)

I have to agree, please don't merge the two. In Microbiology, they are two distinct pathways!

  • Good debate! I will take down the merge tags, although there are clarification issues which need to be addressed for the casual reader. Thank you for your comments :) - Zephyris Talk 00:02, 12 December 2006 (UTC)

From an exercise/physical therapy perspective, the two topics are very different. We do not talk about fermentation occurring during exercise.

  • It is a valid point that under different circumstances these terms carry different meanings, however because not all situations use them interchangably or misuse them according to some definitions they deserve separate pages. The page essentially needs a large restructure with sections for each major use of the term 'anaerobic respiration' and an explanation of its use in that situation.
In the case you mention it may be as simple as putting "For the process of anaerobic respiration in mammalian (human) muscle see: Fermentation (biochemistry)"... In fact, I think ill do that! - Zephyris Talk 23:15, 12 December 2006 (UTC)
I would edit it but im having bizzarre problems with my keyboard... I have edited fermentation (biochemistry) to emphasise its position as anaerobic respiration with no external electron acceptor. - Zephyris Talk 23:58, 12 December 2006 (UTC)

Energy released?[edit]

This cites the energy released as 120 kJ - is that supposed to be kilojoules (way too high), kilojoules/mole, some other unit than kJ? What's the deal?


Why is this page being vandalised on a regular basis? JFW | T@lk 22:26, 13 Nov 2004 (UTC)

Probably just young kids at school etc. —Preceding unsigned comment added by (talk) 12:04, 19 May 2008 (UTC)

No O2 in Krebs'[edit]

There is no O2 within the action of the Krebs' Cycle, but only takes place under aerobic conditions. How is this?

It's because the Krebs' cycle will not advance without NAD+. JFW | T@lk 09:12, 17 Dec 2004 (UTC)

Isn't there also 'anaerobic respiratiyon' using sulphide or nitrogen containing molecules?

Doesn't it say that, even if only briefly. See Anaerobic_respiration#Fermentation_in_other_organisms David D. (Talk) 13:30, 12 July 2006 (UTC)

For prokaryotes you have (a) aerobic respiration, (b) fermentation, AND (c) anaerobic respiration 1. Anaerobic respiration IS NOT FERMENTATION; 2. Oxidative phosphorylation occurs with or without oxygen; 3. THERE IS A KREBS CYCLE (albeit modified) in anaerobic respiration!; 4. NAD+ IS recirculated from an anaerobic electron transport chain as electron acceptors other than O2 are used - cytochromes and ubiquinones are still present to accept electrons from NADH allowing the oxidation of NADH back into NAD+; 5. ATP yields using anaerobic respiration are much less than the max. theoretical prokaryotic yield of 38, but it is also way more than the 2 resulting from fermentation. (talk) 22:28, 23 April 2009 (UTC)M. Lewis


What on earth does this mean: "The end product of fermentation in C. perfringens is a gas which causes the condition of gas. When the Oxygen levels are low, it takes turn to give out a β helix."

I deleted these two sentences since C. perfringens carries out fermentation, not anaerobic respiration. NighthawkJ 17:49, 28 November 2006 (UTC)

+ Addition (jccnoon (Talk)) This article is far too technical and specialized, it should have at the very least an alternative introduction for those with less of an understanding in the field.

+ Agreed. I was looking for a quick way to understand how it is that an alligator produces its energy without oxygen. IE A drug is injected into the bloodstream as opposed to air? —Preceding unsigned comment added by (talk) 05:19, 7 July 2008 (UTC)

+ This should be simplified to where highschool students can at least get an understanding -- at its current state, you can't. — Preceding unsigned comment added by (talk) 02:35, 3 November 2014 (UTC)

Unclickable metabolic map[edit]

The disclosable metabolic map insert at the bottom has a legend that says the pathways are clickable, but they are *not*. How to correct this? Does anyone know? Rudd-O 01:28, 5 June 2007 (UTC)

Respiration is NOT the same as Fermentation[edit]

Respiration (be it aerobic or anaerobic) is fundamentally different from fermentation and I join whoever is disputing the factual accuracy of this article as the article is at the very least ambiguous about clearly differentiating between the two. I can provide further details and references at a leter time, but I just wanted to put this out there now try to warn readers from assuming that all the information presented is true and reliable. I also fully oppose any suggestions to merge this topic with fermentation.

DocMelvis (talk) 06:50, 26 April 2008 (UTC)

Hi I am student (no doctor!) So basically I dont understand is that does Lactic Acid really release more energy? —Preceding unsigned comment added by (talk) 16:05, 19 November 2008 (UTC)

I second DocMelvis: Respiration is NOT the same as Fermentation[edit]

The article is factually inaccurate and fundamentally misunderstands respiration. For the most part it describes fermentation, which is very different from respiration. Respiration is the transfer of electrons (typically from NADH) to an electron-receptor while at the same time creating a proton-gradient across a membrane. The proton-motive force of this gradient can then be used to drive ATP synthesis for example via FoF1 ATPase. So a) this article should definitely not be merged with respiration and b) needs to be changed. The factual correct part starts after Anaerobic respiration in prokaryotes. I'll change it, if I have the time... For now I just changed the reason of the dispute so that readers are alerted.

--Salzbrot (talk) 21:10, 27 November 2008 (UTC)

I rewrote the lead and removed the sections describing fermentation. Clearly, the remaining sections should be expanded. I am also finding the same factual inaccuracies described in related wikipedia articles such as Cellular respiration, which I'll try to correct. NighthawkJ (talk) 00:55, 29 November 2008 (UTC)
I fixed the template. Tim Vickers (talk) 17:04, 29 November 2008 (UTC)

Anaerobic respiration IS the same as fermentation. Unfortunately the article is describing AEROBIC respiration. I'm sorry, I am not really sure how to use wikipedia, I just wanted to clear things up. —Preceding unsigned comment added by (talk) 02:54, 2 March 2009 (UTC)

Anaerobic respiration IS NOT fermentation. Check any Biochemistry or Microbiology textbook (e. Stryer's or Lehninger's Biochemitry or Brock's Biology of the Microorganisms, IIRC) It is also not true that respiration always forms a transmembrane electrochemical gradient. In fermentation, NAD+ is regenerated by electron-transfer form NADH to an electron acceptor produced in the same metabolic pathway, whereas in respiration, the electron acceptor is a chemical speicies that comes from outside the metabolism that yielded the NADH. —Preceding unsigned comment added by (talk) 10:50, 12 February 2010 (UTC)

Factual inconsistency[edit]

Could an expert please resolve the following contradiction: This article states that:

"Anaerobic respiration should therefore not be confused with fermentation, as in ethanol fermentation and lactic acid fermentation."

The Wikipedia article on lactic acid fermentation states that:

"It [lactic acid fermentation] is the anaerobic form of respiration that occurs in some bacteria..."  —Preceding unsigned comment added by (talk) 17:57, 22 March 2010 (UTC) 

Lactic acid fermentation[edit]

Although it is well-written, I removed the section of lactate in humans as it has nothing to do with anaerobic respiration. This content could be added to fermentation instead. Rainbowwrasse (talk) 15:50, 6 July 2011 (UTC)

Suggestions concerning fermentation[edit]

Hello, I understand that by your definitions fermentation is not considered a form of anaerobic respiration because the oxidizing species is regenerated and "not supplied externally". However, I do not agree that this is the accepted convention, on the contrary I think that most biologists will not distinguish between the two in such a way, if at all. Furthermore, the article does not address this convention well. I do not understand how a cell can "generate" an oxidizing agent without reducing something else with a higher reduction potential, meaning that at some point an external oxidizing agent must be supplied to maintain the system (this is basic redox chemistry). In fermentation, pyruvate serves as the final electron acceptor (from NADH), producing lactic acid, ethanol, etc. so glucose (supplied externally of course) is technically the source of the oxidizing agent. I think that to say they differ in that anaerobic respiration acts just like aerobic respiration utilizing an electron transport chain situated across a membrane to transport electrons to a final species other than oxygen would be much more correct. I think that including the section differentiating aerobic respiration from fermentation should be removed, because like I said, they differ in convention more-so than in mechanism and this is not addressed. I think people looking for a straightforward article for a simple topic will find themselves confused or turning to other sources, particularly because most students are introduced to anaerobic respiration via the topics of glycolysis and fermentation.

UPDATE: I edited the fermentation section to address these issues

PedroLZamora (talk) 01:30, 18 December 2011 (UTC) Pedro Zamora

Fermentation (in the biochemical rather than in the industrial sense) is by definition not a form of anaerobic respiration, and this is the accepted convention among biologists. However you are correct in saying that the definition is independent of whether or not the oxidizing species is generated by the organism or not (cf. fumarate respiration), but rather by the use of an electron transport chain and a the generation of a trans-membrane gradient. This is stated right at the start of the article. I think your changes clarify this difference very well, but only illustrate the defining difference, not other general differences. The point of the section is to compare the two in general, not to simply give a definition. In your example of glucose fermentation there is no 'external' oxidant as glucose ultimately provides both the oxidant and the reductant. Electrons stripped from glyceraldehyde 3 phosphate are later dumped back onto pyruvate. The electrons are shuffled around a bit, but stay within the system unless they can be dumped somewhere else. The need to dispose of surplus electrons to regenerate NAD(P) is a pretty major requirement and a difference to respiration, where the point is not so much the regeneration of electron acceptors, but rather the generation of eg. a proton motive force. If people find themselves confused by the complexity of a topic they were hoping would be simpler then this is unfortunate, but does not warrant an over-simplification to the point where fermentation and anaerobic respiration are conflated. If most students are introduced to anaerobic respiration via fermentation, and see them as equivalent, then they are simply not being informed very well, and such erroneous assumptions should be corrected in the article, rather than be reinforced. Rainbowwrasse (talk) 00:55, 11 March 2012 (UTC)

Anoxic Respiration?[edit]

What about anoxic respiration? That is, respiration with electron acceptors that have bound oxygen like nitrate and sulfate which this wiki refer to but would not be classified as anaerobic under current definitions.

As of now the term "anoxic respiration" does not return any results.

The "Anoxic waters" wiki refers to respiration of nitrate and sulfate as well. I believe the misuse of the term anaerobic in situations that are actually anoxic is one that is troubling a lot of people. It would be nice to get this cleared up. — Preceding unsigned comment added by (talk) 04:56, 7 November 2015 (UTC)


I agree that my sense is that in the literature, anaerobic respiration is used to refer to pathways that use an external electron acceptor other than oxygen (and an ETC, etc. as with aerobic respiration). This is distinct from fermentation.

However, there are two problems I see: 1) the term anaerobic respiration is used to refer to fermentation on numerous websites; 2) the article is short on sources (with only two plus one unnumbered), two of which are quite old.

I think this article needs to address (specifically refer to) the confusion over this term, and not just define the two pathways as if that is the obvious and common usage. I also think the article needs more sources. I do not think we can allow such a definitive statement about the definition of terms that are used variously without some solid sources. Does anyone have any?Michaplot (talk) 19:48, 11 April 2016 (UTC)

Assessment comment[edit]

The comment(s) below were originally left at Talk:Anaerobic respiration/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Last edited at 01:53, 19 March 2009 (UTC). Substituted at 07:40, 29 April 2016 (UTC)

2016 Rewrite[edit]

I have attempted to improve this article, removing overly technical jargon and updating links to other Wikipedia pages on microorganisms and processes that depend on anaerobic respiration. Hopefully the distinction between anaerobic respiration and fermentation is now clear, even to a non-expert, although a person with very little biology background may still not grasp the concept with more general background on respiration and ATP. The discussion of the proton motive force may still be too technical and could be edited further. S L Seston (talk) 16:09, 19 June 2016 (UTC)