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Encyclopedia > Primary nutritional groups

An organism may be placed into one each of the three pairs of major nutritional groups based on their carbon, energy, and electron sources. In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ...

  • Carbon source refers to the source of carbon used by an organism for growth and development. An organism is defined as heterotrophic when using organic substrates to get its carbon for growth and development, whereas it is autotrophic, when its source of carbon is carbon dioxide(CO2).
  • Reducing equivalent source refers to the necessity of deriving reducing equivalents (electrons) from environmental sources to be used in biosynthetic pathways (e. g. in the form of NADH or NADPH). An organism is defined as organotrophic when it uses organic compounds as source of electrons, whereas it is defined as lithotrophic when it uses inorganic compounds. Organotrophic organisms are often also heterotrophic, using organic compounds as sources of electrons and carbon at the same time. Similarly, lithotrophic organisms are often also autotrophic, using inorganic sources of electrons and (CO2) as inorganic carbon source.
  • Energy source refers to the pathways used by the organism to produce ATP, which is required for fueling the anabolic pathways for biosynthesis of the constituents of the cell. An organism is defined phototrophic when it uses light as energy source, whereas it is chemotrophic when it conserves energy from reactions of chemical compounds.

The basis for energy metabolism of most chemotrophic organisms are oxidation-reduction reactions in which electrons move from an electron donor to an electron acceptor. Energy is released during the reaction. Therefore, compounds used as electron donors by chemotrophs must be diverted into both energy-yielding oxidative pathways and biosynthetic reductive pathways. The range of possible pairs of electron donors and acceptors for chemotrophs is limited to those whose reaction is exergonic enough to conserve enough energy for the transition of at least one proton over a membrane (equals to -15 to -20 kJ/mol). In contrast, phototrophs may use any electron donor and can even catalyse highly endergonic reactions (e. g. the photosynthetic production of starch from water and CO2). A heterotroph (Greek heteron = (an)other and trophe = nutrition) is an organism that requires organic substrates to get its carbon for growth and development. ... An autotroph (in Greek eauton = self and trophe = nutrition) is an organism that produces organic compounds from carbon dioxide as a carbon source, using either light or reactions of inorganic chemical compounds as a source of energy. ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Phototrophs or photoautotrophs are photosynthetic algae, fungi, bacteria and cyanobacteria which build up carbon dioxide and water into organic cell materials using energy from sunlight. ... Chemotrophs are organisms that obtain food (and therefore energy) from breaking down chemicals in their environments. ... The most fundamental reactions in chemistry are the redox processes. ...


It should be noted that the terms aerobic respiration, anaerobic respiration and fermentation are not referring to primary nutritional groups, but simply reflect the different use of possible electron acceptors in the energy metabolism of chemotrophic organisms, such as O2 (aerobic respiration), NO3-, SO42- (), or fumarate(anaerobic respiration), or intrinsic metabolic intermediates (fermentation). Anaerobic respiration refers to the oxidation of molecules in the absence of oxygen to produce energy. ... In its strictest sense, fermentation (formerly called zymnosis) is the anaerobic metabolic breakdown of a nutrient molecule, such as glucose, without net oxidation. ...


Examples

All sort of combinations may exist in nature. For example a cyanobacteria is photolithotrophic, and fungi are chemo-organo-heterotrophic. Eucaryotes are generally easy to categorise. All animals are heterotrophic, as are fungi. Plants are photoautotrophic. However, some eucaryotic microorganisms are not limited to just one nutritional mode. For example, there are some algae that live photolithoautotrophically in the light, but shift to chemoorganoheterotophic life in the dark, and even higher plants retained their ability to respire heterotrophically on the starch at night, which has been synthesised phototrophically during the day. A chemoorganoheterotrophic organism is one that requires organic substrates to get its energy from oxido-reduction of an organic compound. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Protista A eukaryote (also spelled eucaryote) is an organism with complex cells, in which the genetic material is organized into membrane-bound nuclei. ...


On the contrary, procaryotes show a great diversity of nutritional categories. For example, purple S bacteria, or cyanobacteria are photolithoautotrophic, purple non-sulfur bacteria are photoorganoheterotrophic. Some bacteria are limited to only one nutritional group, whereas others are facultative and switch from one mode to the other, depending on the nutrient sources available. For example, archeobacteria are chemo-organo and/or chemo-litho autotrophic. Prokaryotes (from Old Greek pro- before + karyon nut, referring to the cell nucleus, + suffix -otos, pl. ... Purple bacteria are proteobacteria that are phototrophic, i. ... Phyla / Classes Phylum Crenarchaeota Phylum Euryarchaeota     Halobacteria     Methanobacteria     Methanococci     Methanopyri     Archaeoglobi     Thermoplasmata     Thermococci Phylum Korarchaeota Phylum Nanoarchaeota The Archaea are a major division of living organisms. ...


  Results from FactBites:
 
Primary nutritional groups - Wikipedia, the free encyclopedia (587 words)
An organism may be placed into one each of the three pairs of major nutritional groups based on their carbon, energy, and electron sources.
Some eukaryotic microorganisms, however, are not limited to just one nutritional mode.
Some bacteria are limited to only one nutritional group, whereas others are facultative and switch from one mode to the other, depending on the nutrient sources available.
Primary carnitine deficiency - Genetics Home Reference (672 words)
Primary carnitine deficiency is a condition that prevents the body from using fats for energy, particularly during periods without food (fasting).
The incidence of primary carnitine deficiency in the general population is approximately 1 in 100,000 newborns.
Mutations in the SLC22A5 gene cause primary carnitine deficiency.
  More results at FactBites »

 
 

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