Editing Heterotroph (section)

==Ecology==
{{Main|Consumer (food chain)}}

Many heterotrophs are [[Organotroph|chemoorganoheterotrophs]] that use organic carbon (e.g. glucose) as their carbon source, and organic chemicals (e.g. carbohydrates, lipids, proteins) as their electron sources.<ref>{{cite web |url=http://lmecol.evsc.virginia.edu/pubs/C13-Mills_Bull%20Econ%20Geol%20.PDF |title=The role of bacteria in environmental geochemistry |last1=Mills |first1=A.L. |access-date=19 November 2017 |archive-date=6 April 2019 |archive-url=https://web.archive.org/web/20190406194730/https://lmecol.evsc.virginia.edu/pubs/C13-Mills_Bull%20Econ%20Geol%20.PDF |url-status=dead }}</ref> Heterotrophs function as [[Consumer (food chain)|consumers in food chain]]: they obtain these nutrients from [[Saprotrophic nutrition|saprotrophic]], [[Parasitic nutrition|parasitic]], or [[Holozoic nutrition|holozoic nutrients]].<ref>{{cite web |url=https://www.int-res.com/articles/meps/22/m022p101.pdf |archive-url=https://web.archive.org/web/20110524124225/http://www.int-res.com/articles/meps/22/m022p101.pdf |archive-date=2011-05-24 |url-status=live |title=Heterotrophic nutrition and control of bacterial density |access-date=19 November 2017}}</ref> They break down complex organic compounds (e.g., carbohydrates, fats, and proteins) produced by autotrophs into simpler compounds (e.g., carbohydrates into [[glucose]], fats into [[fatty acids]] and [[glycerol]], and proteins into [[amino acids]]). They release the chemical energy of nutrient molecules by oxidizing carbon and hydrogen atoms from carbohydrates, lipids, and proteins to carbon dioxide and water, respectively.

They can catabolize organic compounds by respiration, fermentation, or both. [[Fermentation|Fermenting]] heterotrophs are either facultative or obligate [[Anaerobic organism|anaerobes]] that carry out fermentation in low oxygen environments, in which the production of ATP is commonly coupled with [[substrate-level phosphorylation]] and the production of end products (e.g. alcohol, {{CO2}}, sulfide).<ref name=":0">{{cite book |title=Bacterial Metabolism |last1=Gottschalk |first1=Gerhard |year=2012 |publisher=Springer |isbn=978-0387961538 |edition=2 |doi=10.1007/978-1-4612-1072-6 |series=Springer Series in Microbiology |s2cid=32635137 |url-access=registration |url=https://archive.org/details/bacterialmetabol0000gott }}</ref> These products can then serve as the substrates for other bacteria in the [[Anaerobic digestion|anaerobic digest]], and be converted into CO<sub>2</sub> and CH<sub>4</sub>, which is an important step for the [[carbon cycle]] for removing organic fermentation products from anaerobic environments.<ref name=":0" /> Heterotrophs can undergo [[Cellular respiration|respiration]], in which ATP production is coupled with [[oxidative phosphorylation]].<ref name=":0" /><ref name=":2">{{cite book |title=MICB 201: Introductory Environmental Microbiology |last1=Wade |first1=Bingle |year=2016 |pages=236–250}}</ref> This leads to the release of oxidized carbon wastes such as CO<sub>2</sub> and reduced wastes like H<sub>2</sub>O, H<sub>2</sub>S, or N<sub>2</sub>O into the atmosphere. Heterotrophic microbes' respiration and fermentation account for a large portion of the release of CO<sub>2</sub> into the atmosphere, making it available for autotrophs as a source of nutrient and plants as a cellulose synthesis substrate.<ref name=":1">{{cite book |title=Processes in Microbial Ecology |last1=Kirchman |first1=David L. |year=2014 |publisher=Oxford University Press |place=Oxford |isbn=9780199586936|pages=79–98}}</ref><ref name=":2"/>

Respiration in heterotrophs is often accompanied by [[Mineralization (biology)|mineralization]], the process of converting organic compounds to inorganic forms.<ref name=":1" /> When the organic nutrient source taken in by the heterotroph contains essential elements such as N, S, P in addition to C, H, and O, they are often removed first to proceed with the oxidation of organic nutrient and production of ATP via respiration.<ref name=":1" /> S and N in organic carbon source are transformed into H<sub>2</sub>S and NH<sub>4</sub><sup>+</sup> through desulfurylation and [[deamination]], respectively.<ref name=":1" /><ref name=":2" /> Heterotrophs also allow for [[dephosphorylation]] as part of [[decomposition]].<ref name=":2" /> The conversion of N and S from organic form to inorganic form is a critical part of the [[Nitrogen cycle|nitrogen]] and [[sulfur cycle]]. H<sub>2</sub>S formed from desulfurylation is further oxidized by lithotrophs and phototrophs while NH<sub>4</sub><sup>+</sup> formed from deamination is further oxidized by lithotrophs to the forms available to plants.<ref name=":1" /><ref name=":2" /> Heterotrophs' ability to mineralize essential elements is critical to plant survival.<ref name=":2" />

Most [[opisthokont]]s and [[prokaryote]]s are heterotrophic; in particular, all animals and fungi are heterotrophs.<ref name="cell">{{cite web |url=http://highered.mcgraw-hill.com/sites/dl/free/0072965819/415836/rav65819_ch07.pdf |title=How Cells Harvest Energy |publisher=[[McGraw Hill Education|McGraw-Hill Higher Education]] |access-date=2010-10-10 |archive-url=https://web.archive.org/web/20120731144141/http://highered.mcgraw-hill.com/sites/dl/free/0072965819/415836/rav65819_ch07.pdf |archive-date=2012-07-31 |url-status=dead}}</ref> Some animals, such as [[coral]]s, form [[symbiosis|symbiotic]] relationships with autotrophs and obtain organic carbon in this way. Furthermore, some [[parasitic plant]]s have also turned fully or partially heterotrophic, while [[carnivorous plant]]s consume animals to augment their nitrogen supply while remaining autotrophic.

Animals are classified as heterotrophs by ingestion, fungi are classified as heterotrophs by absorption.