Anaerobic respiration - wikipedia Anaerobic respiration Anaerobic respiration is respiration using electron acceptors other than molecular oxygen ( O ). Although oxygen is not used as the final electron acceptor, the process still uses a respiratory electron transport chain called physolmere ; it is respiration without oxygen. In aerobic organisms undergoing respiration, electrons are shuttled to an electron transport chain, and the final electron acceptor is oxygen. Molecular oxygen is a highly oxidizing agent and, therefore, is an excellent electron acceptor. In anaerobes, other less - oxidizing substances such as sulfate ( SO ), nitrate ( NO ), sulphur ( S ), or fumarate are used. These terminal electron acceptors have smaller reduction potentials than O, meaning that less energy is released per oxidized molecule. Therefore, generally speaking, anaerobic respiration is less efficient than aerobic. Contents 1 Anaerobic respiration as compared with fermentation 2 Ecological importance 3 Economic relevance 4 Examples of respiration 5 See also 6 References Anaerobic respiration as compared with fermentation There are two important microbial methane formation pathways, through carbonate reduction ( respiration ), and acetate fermentation. Cellular respiration ( both aerobic and anaerobic ) utilizes highly reduced chemical compounds such as NADH and FADH2 ( for example produced during glycolysis and the citric acid cycle ) to establish an electrochemical gradient ( often a proton gradient ) across a membrane, resulting in an electrical potential or ion concentration difference across the membrane. The reduced chemical compounds are oxidized by a series of respiratory integral membrane proteins with sequentially increasing reduction potentials with the final electron acceptor being oxygen ( in aerobic respiration ) or another chemical substance ( in anaerobic respiration ). A proton motive force drives protons down the gradient ( across the membrane ) through the proton channel of ATP synthase. The resulting current drives ATP synthesis from ADP and inorganic phosphate. Fermentation, in contrast, does not utilize an electrochemical gradient. Fermentation instead only uses substrate - level phosphorylation to produce ATP. The electron acceptor NAD+ is regenerated from NADH formed in oxidative steps of the fermentation pathway by the reduction of oxidized compounds. These oxidized compounds are often formed during the fermentation pathway itself, but may also be external. For example, in homofermentative lactic acid bacteria, NADH formed during the oxidation of glyceraldehyde - 3 - phosphate is oxidized back to NAD+ by the reduction of pyruvate to lactic acid at a later stage in the pathway. In yeast, acetaldehyde is reduced to ethanol to regenerate NAD+. The two processes thus generate ATP in very different ways, and the terms should not be treated as synonyms. Ecological importance Anaerobic respiration is a critical component of the global nitrogen, iron, sulfur, and carbon cycles through the reduction of the oxyanions of nitrogen, sulfur, and carbon to more - reduced compounds. The biogeochemical cycling of these compounds, which depends upon anaerobic respiration, significantly impacts the carbon cycle and global warming. Anaerobic respiration occurs in many environments, including freshwater and marine sediments, soil, subsurface aquifers, deep subsurface environments, and biofilms. Even environments, such as soil, that contain oxygen also have micro-environments that lack oxygen due to the slow diffusion characteristics of oxygen gas. An example of the ecological importance of anaerobic respiration is the use of nitrate as a terminal electron acceptor, or dissimilatory denitrification, which is the main route by which fixed nitrogen is returned to the atmosphere as molecular nitrogen gas. Another example is methanogenesis, a form of carbonate respiration, that is used to produce methane gas by anaerobic digestion. Biogenic methane is used as a sustainable alternative to fossil fuels. On the negative side, uncontrolled methanogenesis in landfill sites releases large volumes of methane into the atmosphere, where it acts as a powerful greenhouse gas. Sulfate respiration produces hydrogen sulfide, which is responsible for the characteristic ' rotten egg ' smell of coast wetlands and has the capacity to precipitate heavy metal ions from solution, leading to the deposition of sulfidic metal ores. Economic relevance Dissimilatory denitrification is widely used in the removal of nitrate and nitrite from municipal wastewater. An excess of nitrate can lead to eutrophication of waterways into which treated water is released. Elevated nitrite levels in drinking water can lead to problems due to its toxicity. Denitrification converts both compounds into harmless nitrogen gas. Specific types of anaerobic respiration are also critical in bioremediation, which uses microorganisms to convert toxic chemicals into less - harmful molecules to clean up contaminated beaches, aquifers, lakes, and oceans. For example, toxic arsenate or selenate can be reduced to less toxic compounds by various anaerobic bacteria via anaerobic respiration. The reduction of chlorinated chemical pollutants, such as vinyl chloride and carbon tetrachloride, also occurs through anaerobic respiration. Anaerobic respiration is useful in generating electricity in microbial fuel cell s, which employ bacteria that respire solid electron acceptors ( such as oxidized iron ) to transfer electrons from reduced compounds to an electrode. This process can simultaneously degrade organic carbon waste and generate electricity. Examples of respiration Type Lifestyle Electron acceptor Products E ( V ) Example organisms aerobic respiration obligate aerobes and facultative anaerobes O H O + 0.82 eukaryotes and aerobic prokaryotes iron reduction facultative anaerobes and obligate anaerobes Fe ( III ) Fe ( II ) + 0.75 Organisms within the order Desulfuromonadales ( such as Geobacter, Geothermobacter, Geopsychrobacter, Pelobacter ) and Shewanella species manganese facultative anaerobes and obligate anaerobes Mn ( IV ) Mn ( II ) Desulfuromonadales and Shewanella species cobalt reduction facultative anaerobes and obligate anaerobes Co ( III ) Co ( II ) Geobacter sulfurreducens uranium reduction facultative anaerobes and obligate anaerobes U ( VI ) U ( IV ) Geobacter metallireducens, Shewanella oneidensis nitrate reduction ( denitrification ) facultative anaerobes nitrate NO nitrite NO + 0.40 Paracoccus denitrificans, Escherichia coli fumarate respiration facultative anaerobes fumarate succinate + 0.03 Escherichia coli sulfate respiration obligate anaerobes sulfate SO sulfide HS - 0.22 Many Deltaproteobacteria species in the orders Desulfobacterales, Desulfovibrionales, and Syntrophobacterales methanogenesis ( carbonate reduction ) methanogens carbon dioxide CO methane CH - 0.25 Methanosarcina barkeri sulfur respiration ( sulfur reduction ) facultative anaerobes and obligate anaerobes sulfur S sulfide HS - 0.27 Desulfuromonadales acetogenesis ( carbonate reduction ) obligate anaerobes carbon dioxide CO acetate - 0.30 Acetobacterium woodii dehalorespiration facultative anaerobes and obligate anaerobes halogenated organic compounds R-X Halide ions and dehalogenated compound X + R-H + 0.25 -- + 0.60 Dehalococcoides and Dehalobacter species See also Hydrogenosomes and mitosomes Standard electrode potential ( data page ) Table of standard reduction potentials for half - reactions important in biochemistry References Jump up ^ Slonczewski, Joan L. ; Foster, John W. ( 2011 ). Microbiology : An Evolving Science ( 2nd ed. ). New York : W.W. Norton. p. 166. ISBN 9780393934472. Jump up ^ Sapart ; et al. ( 2017 ). `` The origin of methane in the East Siberian Arctic Shelf unraveled with triple isotope analysis ''. Biogeosciences. doi : 10.5194 / bg - 14 - 2283 - 2017. CS1 maint : Explicit use of et al. ( link ) Jump up ^ Simon, Jörg ; Klotz, Martin G. ( 2013 - 02 - 01 ). `` Diversity and evolution of bioenergetic systems involved in microbial nitrogen compound transformations ''. Biochimica et Biophysica Acta ( BBA ) - Bioenergetics. The evolutionary aspects of bioenergetic systems. 1827 ( 2 ) : 114 -- 135. doi : 10.1016 / j. bbabio. 2012.07. 005. Jump up ^ Bogner, Jean ; Pipatti, Riitta ; Hashimoto, Seiji ; Diaz, Cristobal ; Mareckova, Katarina ; Diaz, Luis ; Kjeldsen, Peter ; Monni, Suvi ; Faaij, Andre ( 2008 - 02 - 01 ). `` Mitigation of global greenhouse gas emissions from waste : conclusions and strategies from the Intergovernmental Panel on Climate Change ( IPCC ) Fourth Assessment Report. Working Group III ( Mitigation ) ''. Waste management & research : the journal of the International Solid Wastes and Public Cleansing Association, ISWA. 26 ( 1 ) : 11 -- 32. doi : 10.1177 / 0734242x07088433. ISSN 0734 - 242X. PMID 18338699. Jump up ^ Pester, Michael ; Knorr, Klaus - Holger ; Friedrich, Michael W. ; Wagner, Michael ; Loy, Alexander ( 2012 - 01 - 01 ). `` Sulfate - reducing microorganisms in wetlands - fameless actors in carbon cycling and climate change ''. Frontiers in Microbiology. 3 : 72. doi : 10.3389 / fmicb. 2012.00072. ISSN 1664 - 302X. PMC 3289269. PMID 22403575. Jump up ^ Nancharaiah, Y.V. ; Venkata Mohan, S. ; Lens, P.N.L. ( 2016 - 09 - 01 ). `` Recent advances in nutrient removal and recovery in biological and bioelectrochemical systems ''. Bioresource Technology. 215 : 173 -- 185. doi : 10.1016 / j. biortech. 2016.03. 129. ISSN 1873 - 2976. PMID 27053446. Jump up ^ Xu, Bojun ; Ge, Zheng ; He, Zhen ( 2015 - 05 - 15 ). `` Sediment microbial fuel cells for wastewater treatment : challenges and opportunities ''. Environ. Sci. : Water Res. Technol. 1 ( 3 ) : 279 -- 284. doi : 10.1039 / c5ew00020c. ISSN 2053 - 1419. ^ Jump up to : Richter, Katrin ; Schicklberger, Marcus ; Gescher, Johannes ( 2012 - 02 - 01 ). `` Dissimilatory reduction of extracellular electron acceptors in anaerobic respiration ''. Applied and Environmental Microbiology. 78 ( 4 ) : 913 -- 921. doi : 10.1128 / AEM. 06803 - 11. ISSN 1098 - 5336. PMC 3273014. PMID 22179232. Jump up ^ Holliger, C. ; Wohlfarth, G. ; Diekert, G. ( 1998 ). `` Reductive dechlorination in the energy metabolism of anaerobic bacteria ''. FEMS Microbiology Reviews. 22 ( 5 ) : 383. doi : 10.1111 / j. 1574 - 6976.1998. tb00377. x. Metabolism, catabolism, anabolism General Metabolic pathway Metabolic network Primary nutritional groups Energy metabolism Aerobic respiration Glycolysis → Pyruvate decarboxylation → Citric acid cycle → Oxidative phosphorylation ( electron transport chain + ATP synthase ) Anaerobic respiration Electron acceptors are other than oxygen Fermentation Glycolysis → Substrate - level phosphorylation ABE Ethanol Lactic acid Specific paths Protein metabolism Protein synthesis Catabolism Carbohydrate metabolism ( carbohydrate catabolism and anabolism ) Human Glycolysis ⇄ Gluconeogenesis Glycogenolysis ⇄ Glycogenesis Pentose phosphate pathway Fructolysis Galactolysis Glycosylation N - linked O - linked Nonhuman Photosynthesis Anoxygenic photosynthesis Chemosynthesis Carbon fixation Xylose metabolism Radiotrophism Lipid metabolism ( lipolysis, lipogenesis ) Fatty acid metabolism Fatty acid degradation ( Beta oxidation ) Fatty acid synthesis Other Steroid metabolism Sphingolipid metabolism Eicosanoid metabolism Ketosis Reverse cholesterol transport Amino acid Amino acid synthesis Urea cycle Nucleotide metabolism Purine metabolism Nucleotide salvage Pyrimidine metabolism Other Metal metabolism Iron metabolism Ethanol metabolism Metabolism map Carbon Fixation Photo - respiration Pentose Phosphate Pathway Citric Acid Cycle Glyoxylate Cycle Urea Cycle Fatty Acid Synthesis Fatty Acid Elongation Beta Oxidation Peroxisomal Beta Oxidation Glyco - genolysis Glyco - genesis Glyco - lysis Gluconeo - genesis Decarb - oxylation Fermentation Keto - lysis Keto - genesis feeders to Gluconeo - genesis Direct / C4 / CAM Carbon Intake Light Reaction Oxidative Phosphorylation Amino Acid Deamination Citrate Shuttle Lipogenesis Lipolysis Steroidogenesis MVA Pathway MEP Pathway Shikimate Pathway Transcription & Replication Translation Proteolysis Glycosy - lation Sugar Acids Double / Multiple Sugars & Glycans Simple Sugars Inositol - P Amino Sugars & Sialic Acids Nucleotide Sugars Hexose - P Triose - P Glycerol P - glycerates Pentose - P Tetrose - P Propionyl - CoA Succinate Acetyl - CoA Pentose - P P - glycerates Glyoxylate Photosystems Pyruvate Lactate Acetyl - CoA Citrate Oxalo - acetate Malate Succinyl - CoA α - Keto - glutarate Ketone Bodies Respiratory Chain Serine Group Alanine Branched - chain Amino Acids Aspartate Group Homoserine Group & Lysine Glutamate Group & Proline Arginine Creatine & Polyamines Ketogenic & Glucogenic Amino Acids Amino Acids Shikimate Aromatic Amino Acids & Histidine Ascorbate ( Vitamin C ) δ - ALA Bile Pigments Hemes Cobalamins ( Vitamin B ) Various Vitamin B 's Calciferols ( Vitamin D ) Retinoids ( Vitamin A ) Quinones ( Vitamin K ) & Carotenoids ( Vitamin E ) Cofactors Vitamins & Minerals Antioxidants PRPP Nucleotides Nucleic Acids Proteins Glycoproteins & Proteoglycans Chlorophylls MEP MVA Acetyl - CoA Polyketides Terpenoid Backbones Terpenoids & Carotenoids ( Vitamin A ) Cholesterol Bile Acids Glycero - phospholipids Glycerolipids Acyl - CoA Fatty Acids Glyco - sphingolipids Sphingolipids Waxes Polyunsaturated Fatty Acids Neurotransmitters & Thyroid Hormones Steroids Endo - cannabinoids Eicosanoids Major metabolic pathways in metro - style map. Click any text ( name of pathway or metabolites ) to link to the corresponding article. Single lines : pathways common to most lifeforms. Double lines : pathways not in humans ( occurs in e.g. plants, fungi, prokaryotes ). Orange nodes : carbohydrate metabolism. Violet nodes : photosynthesis. Red nodes : cellular respiration. Pink nodes : cell signaling. Blue nodes : amino acid metabolism. Grey nodes : vitamin and cofactor metabolism. Brown nodes : nucleotide and protein metabolism. Green nodes : lipid metabolism. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Anaerobic_respiration&oldid=818610054 '' Categories : Anaerobic digestion Biodegradation Cellular respiration Hidden categories : CS1 maint : Explicit use of et al. All accuracy disputes Articles with disputed statements from July 2014 Talk Contents About Wikipedia Català Dansk Eesti Ελληνικά Español Euskara Français Galego 한국어 Italiano Magyar മലയാളം Bahasa Melayu 日本 語 Polski Русский Simple English Türkçe Українська Tiếng Việt Edit links This page was last edited on 4 January 2018, at 15 : 21. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: what is the role of anaerobic respiration in living things
Answer: ATP synthesis from ADP and inorganic phosphate; respiration using electron acceptors other than molecular oxygen