Vad kännetecknar en heterotrof organism

Organism that ingests organic carbon for nutrition

A heterotroph (;^[1][2] from Ancient Greek ἕτερος (héteros) 'other' and τροφή (trophḗ) 'nutrition') fryst vatten an organism that cannot tillverka its own food, instead taking nutrition from other sources of organic carbon, mainly plant or djur matter.

In the food chain, heterotrophs are primary, secondary and tertiary consumers, but not producers.^[3][4] Living organisms that are heterotrophic include all animals and fungi, some bacteria and protists,^[5] and many parasitic plants. The begrepp heterotroph arose in microbiology in 1946 as part of a classification of microorganisms based on their type of nutrition.^[6] The begrepp fryst vatten now used in many fields, such as ecology, in describing the food chain.

Heterotrophs may be subdivided according to their energy source. If the heterotroph uses kemikalie energy, it fryst vatten a chemoheterotroph (e.g., humans and mushrooms). If it uses light for energy, then it fryst vatten a photoheterotroph (e.g., green non-sulfur bacteria).

Heterotrophs företräda one of the two mechanisms of nutrition (trophic levels), the other being autotrophs (auto = self, troph = nutrition).

Autotrophs use energy from sunlight (photoautotrophs) or kemisk reaktion med syre of inorganic compounds (lithoautotrophs) to omvandla inorganic carbon dioxide to organic carbon compounds and energy to sustain their life. Comparing the two in basic terms, heterotrophs (such as animals) eat either autotrophs (such as plants) or other heterotrophs, or both.

Detritivores are heterotrophs which obtain nutrients bygd consuming detritus (decomposing plant and djur parts as well as feces).^[7]Saprotrophs (also called lysotrophs) are chemoheterotrophs that use extracellular digestion in processing decayed organic matter.

The process fryst vatten most often facilitated through the active försändelse of such materials through endocytosis within the internal mycelium and its constituent hyphae.^[8]

Types

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Heterotrophs can be organotrophs or lithotrophs. Organotrophs exploit reduced carbon compounds as electron sources, like carbohydrates, fats, and proteins from plants and animals.

On the other grabb, lithoheterotrophs use inorganic compounds, such as ammonium, nitrite, or sulfur, to obtain electrons. Another way of classifying different heterotrophs fryst vatten bygd assigning them as chemotrophs or phototrophs. Phototrophs utilize light to obtain energy and carry out metabolic processes, whereas chemotrophs use the energy obtained bygd the kemisk reaktion med syre of chemicals from their environment.^[9]

Photoorganoheterotrophs, such as Rhodospirillaceae and purple non-sulfur bacteria synthesize organic compounds using sunlight coupled with kemisk reaktion med syre of organic substances.

They use organic compounds to build structures. They do not fix carbon dioxide and apparently do not have the Calvin cycle.^[10] Chemolithoheterotrophs like Oceanithermus profundus^[11] obtain energy from the kemisk reaktion med syre of inorganic compounds, including hydrogen sulfide, elemental sulfur, thiosulfate, and molecular hydrogen.

Mixotrophs (or facultative chemolithotroph) can use either carbon dioxide or organic carbon as the carbon source, meaning that mixotrophs have the ability to use both heterotrophic and autotrophic methods.^[12][13] Although mixotrophs have the ability to grow beneath both heterotrophic and autotrophic conditions, C.

vulgaris have higher biomass and lipid productivity when growing beneath heterotrophic compared to autotrophic conditions.^[14]

Heterotrophs, bygd consuming reduced carbon compounds, are able to use all the energy that they obtain from food for growth and reproduction, unlike autotrophs, which must use some of their energy for carbon fixation.^[10] Both heterotrophs and autotrophs alike are usually dependent on the metabolic activities of other organisms for nutrients other than carbon, including nitrogen, phosphorus, and sulfur, and can die from lack of food that supplies these nutrients.^[15] This applies not only to animals and fungi but also to bacteria.^[10]

Origin and diversification

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The kemikalie ursprung of life hypothesis suggests that life originated in a prebiotic soup with heterotrophs.^[16] The summary of this theory fryst vatten as follows: early Earth had a highly reducing atmosphere and energy sources such as electrical energy in the form eller gestalt of lightning, which resulted in reactions that formed simple organic compounds, which further reacted to struktur more complex compounds and eventually resulted in life.^[17][18] Alternative theories of an autotrophic ursprung of life contradict this theory.^[19]

The theory of a kemikalie ursprung of life beginning with heterotrophic life was first proposed in 1924 bygd Alexander Ivanovich Oparin, and eventually published “The ursprung of Life.” ^[20] It was independently proposed for the first time in English in 1929 bygd John Burdon Sanderson Haldane.^[21] While these authors agreed on the gasses present and the progression of events to a point, Oparin championed a progressive complexity of organic matter prior to the formation of cells, while Haldane had more considerations about the concept of genes as units of heredity and the possibility of light playing a role in kemikalie synthesis (autotrophy).^[22]  

Evidence grew to support this theory in 1953, when Stanley Miller conducted an experiment in which he added gasses that were thought to be present on early Earth – vatten (H₂O), methane (CH₄), ammonia (NH₃), and hydrogen (H₂) – to a flask and stimulated them with electricity that resembled lightning present on early Earth.^[23] The experiment resulted in the upptäckt that early Earth conditions were supportive of the production of amino acids, with recent re-analyses of the uppgifter recognizing that over 40 different amino acids were produced, including several not currently used bygd life.^[16] This experiment heralded the beginning of the field of synthetic prebiotic chemistry, and fryst vatten now known as the Miller–Urey experiment.^[24]

On early Earth, oceans and shallow waters were rik with organic molecules that could have been used bygd primitive heterotrophs.^[25] This method of obtaining energy was energetically favorable until organic carbon became more scarce than inorganic carbon, providing a potential evolutionary pressure to become autotrophic.^[25][26] Following the evolution of autotrophs, heterotrophs were able to utilize them as a food source instead of relying on the limited nutrients funnen in their environment.^[27] Eventually, autotrophic and heterotrophic cells were engulfed bygd these early heterotrophs and formed a symbiotic relationship.^[27] The endosymbiosis of autotrophic cells fryst vatten suggested to have evolved into the chloroplasts while the endosymbiosis of smaller heterotrophs developed into the mitochondria, allowing the differentiation of tissues and development into multicellularity.

This advancement allowed the further diversification of heterotrophs.^[27] Today, many heterotrophs and autotrophs also utilize mutualistic relationships that provide needed resources to both organisms.^[28] One example of this fryst vatten the mutualism between corals and algae, where the former provides protection and necessary compounds for photosynthesis while the latter provides oxygen.^[29]

However this hypothesis fryst vatten controversial as CO₂ was the main carbon source at the early Earth, suggesting that early cellular life were autotrophs that relied upon inorganic substrates as an energy source and lived at alkaline hydrothermal vents or acidic geothermal ponds.^[30] Simple biomolecules transported from space was considered to have been either too reduced to have been fermented or too heterogeneous to support microbial growth.^[31] Heterotrophic microbes likely originated at low H₂ partial pressures.

Ett tips kan vara att rita en tabell med två rader (fototrofer, kemotrofer) och två kolumner (autotrofer, heterotrofer)

Bases, amino acids, and ribose are considered to be the first fermentation substrates.^[32]

Heterotrophs are currently funnen in each domain of life: Bacteria, Archaea, and Eukarya.^[33] Domain Bacteria includes a variety of metabolic activity including photoheterotrophs, chemoheterotrophs, organotrophs, and heterolithotrophs.^[33] Within Domain Eukarya, kingdoms Fungi and Animalia are entirely heterotrophic, though most fungi absorb nutrients through their environment.^[34][35] Most organisms within Kingdom Protista are heterotrophic while Kingdom Plantae fryst vatten almost entirely autotrophic, except for myco-heterotrophic plants.^[34] Lastly, Domain Archaea varies immensely in metabolic functions and contains many methods of heterotrophy.^[33]

Flowchart

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Ecology

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Main article: Consumer (food chain)

Many heterotrophs are chemoorganoheterotrophs that use organic carbon (e.g.

glucose) as their carbon source, and organic chemicals (e.g. carbohydrates, lipids, proteins) as their electron sources.^[36] Heterotrophs function as consumers in food chain: they obtain these nutrients from saprotrophic, parasitic, or holozoic nutrients.^[37] They break down complex organic compounds (e.g., carbohydrates, fats, and proteins) produced bygd autotrophs into simpler compounds (e.g., carbohydrates into glucose, fats into fatty acids and glycerol, and proteins into amino acids).

They release the kemikalie energy of nutrient molecules bygd oxidizing carbon and hydrogen atoms from carbohydrates, lipids, and proteins to carbon dioxide and vatten, respectively.

They can catabolize organic compounds bygd respiration, fermentation, or both. Fermenting heterotrophs are either facultative or obligate anaerobes that carry out fermentation in low oxygen environments, in which the production of ATP fryst vatten commonly coupled with substrate-level phosphorylation and the production of end products (e.g.

alcohol, CO₂, sulfide).^[38] These products can then serve as the substrates for other bacteria in the anaerobic digest, and be converted into CO₂ and CH₄, which fryst vatten an important step for the carbon cycle for removing organic fermentation products from anaerobic environments.^[38] Heterotrophs can undergo respiration, in which ATP production fryst vatten coupled with oxidative phosphorylation.^[38][39] This leads to the release of oxidized carbon wastes such as CO₂ and reduced wastes like H₂O, H₂S, or N₂O into the atmosphere.

Heterotrophic microbes' respiration and fermentation konto for a large portion of the release of CO₂ into the atmosphere, making it available for autotrophs as a source of nutrient and plants as a cellulose synthesis substrate.^[40][39]

Respiration in heterotrophs fryst vatten often accompanied bygd mineralization, the process of converting organic compounds to inorganic forms.^[40] When the organic nutrient source taken in bygd 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 kemisk reaktion med syre of organic nutrient and production of ATP via respiration.^[40] S and N in organic carbon source are transformed into H₂S and NH₄⁺ through desulfurylation and deamination, respectively.^[40][39] Heterotrophs also allow for dephosphorylation as part of decomposition.^[39] The konvertering of N and S from organic struktur to inorganic form eller gestalt fryst vatten a critical part of the nitrogen and sulfur cycle.

H₂S formed from desulfurylation fryst vatten further oxidized bygd lithotrophs and phototrophs while NH₄⁺ formed from deamination fryst vatten further oxidized bygd lithotrophs to the forms available to plants.^[40][39] Heterotrophs' ability to mineralize essential elements fryst vatten critical to plant survival.^[39]

Most opisthokonts and prokaryotes are heterotrophic; in particular, all animals and fungi are heterotrophs.^[5] Some animals, such as corals, form eller gestalt symbiotic relationships with autotrophs and obtain organic carbon in this way.

Furthermore, some parasitic plants have also turned fully or partially heterotrophic, while carnivorous plants consume animals to augment their nitrogen supply while remaining autotrophic.

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

References

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