electron acceptor

(noun)

An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process.

Related Terms

Examples of electron acceptor in the following topics:

  • Electron Donors and Acceptors in Anaerobic Respiration

    • In anaerobic respiration, a molecule other than oxygen is used as the terminal electron acceptor in the electron transport chain.
    • This method still incorporates the respiratory electron transport chain, but without using oxygen as the terminal electron acceptor .
    • Many different types of electron acceptors may be used for anaerobic respiration.
    • Acetogenesis is a type of microbial metabolism that uses hydrogen (H2) as an electron donor and carbon dioxide (CO2) as an electron acceptor to produce acetate, the same electron donors and acceptors used in methanogenesis.
    • Organic compounds may also be used as electron acceptors in anaerobic respiration.

  • Electron Donors and Acceptors

    • In prokaryotes (bacteria and archaea there are several different electron donors and several different electron acceptors.
    • These levels correspond to successively more positive redox potentials, or to successively decreased potential differences relative to the terminal electron acceptor.
    • Bacteria can use a number of different electron donors, a number of different dehydrogenases, a number of different oxidases and reductases, and a number of different electron acceptors.
    • Just as there are a number of different electron donors (organic matter in organotrophs, inorganic matter in lithotrophs), there are a number of different electron acceptors, both organic and inorganic.
    • NADH is the electron donor and O2 is the electron acceptor.

  • Methanogenesis

    • Methanogenesis is a form of anaerobic respiration that uses carbon as a electron acceptor and results in the production of methane.
    • The two best described pathways of methanogenesis use carbon dioxide or acetic acid as the terminal electron acceptor:
    • During advanced stages of organic decay, all electron acceptors become depleted except carbon dioxide, which is a product of most catabolic processes.
    • It is not depleted like other potential electron acceptors.
    • Only methanogenesis and fermentation can occur in the absence of electron acceptors other than carbon.

  • Iron Oxidation

    • Ferric iron is an anaerobic terminal electron acceptor, with the final enzyme a ferric iron reductase.
    • Ferric iron (Fe3+) is a widespread anaerobic terminal electron acceptor both for autotrophic and heterotrophic organisms.
    • Electron flow in these organisms is similar to those in electron transport, ending in oxygen or nitrate, except that in ferric iron-reducing organisms the final enzyme in this system is a ferric iron reductase.
    • Although ferric iron is the most prevalent inorganic electron acceptor, a number of organisms (including the iron-reducing bacteria mentioned above) can use other inorganic ions in anaerobic respiration.
    • While these processes may often be less significant ecologically, they are of considerable interest for bioremediation, especially when heavy metals or radionuclides are used as electron acceptors.

  • Energy Conservation and Autotrophy in Archaea

    • In these reactions one compound passes electrons to another in a redox reaction, releasing energy to fuel the cell's activities.
    • One compound acts as an electron donor and one as an electron acceptor.
    • A common reaction in methanogens involves the use of carbon dioxide as an electron acceptor to oxidize hydrogen.
    • Other organic compounds such as alcohols, acetic acid, or formic acid are used as alternative electron acceptors by methanogens.
    • Besides these, archaeal energy sources are extremely diverse, and range from the oxidation of ammonia by the Nitrosopumilales to the oxidation of hydrogen sulfide or elemental sulfur by species of Sulfolobus, using either oxygen or metal ions as electron acceptors.

  • Nitrate Reduction and Denitrification

    • Denitrification is a type of anaerobic respiration that uses nitrate as an electron acceptor.
    • In anaerobic respiration, denitrification utilizes nitrate (NO3-) as a terminal electron acceptor in the respiratory electron transport chain.
    • In general, it occurs where oxygen is depleted and bacteria respire nitrate as a substitute terminal electron acceptor.

  • Sulfate and Sulfur Reduction

    • Sulfate reduction is a type of anaerobic respiration that utilizes sulfate as a terminal electron acceptor in the electron transport chain.
    • Sulfate reduction is a type of anaerobic respiration that utilizes sulfate as a terminal electron acceptor in the electron transport chain.
    • Many sulfate reducers are organotrophic, using carbon compounds, such as lactate and pyruvate (among many others) as electron donors, while others are lithotrophic, and use hydrogen gas (H2) as an electron donor.
    • Some unusual autotrophic sulfate-reducing bacteria (e.g., Desulfotignum phosphitoxidans) can use phosphite (HPO3-) as an electron donor, whereas others (e.g., Desulfovibrio sulfodismutans, Desulfocapsa thiozymogenes, and Desulfocapsa sulfoexigens) are capable of sulfur disproportionation (splitting one compound into two different compounds, in this case an electron donor and an electron acceptor) using elemental sulfur (S0), sulfite (SO32−), and thiosulfate (S2O32−) to produce both hydrogen sulfide (H2S) and sulfate (SO42−).
    • Before sulfate can be used as an electron acceptor, it must be activated.

  • Oxidoreductase Protein Complexes

    • In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another.
    • In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another the oxidant, also called the electron acceptor.
    • In this example, A is the reductant (electron donor) and B is the oxidant (electron acceptor).
    • In this reaction, NAD+ is the oxidant (electron acceptor) and glyceraldehyde-3-phosphate is the reductant (electron donor).
    • Oxidoreductases can be further classified into 22 subclasses: EC 1.1 includes oxidoreductases that act on the CH-OH group of donors (alcohol oxidoreductases); EC 1.2 includes oxidoreductases that act on the aldehyde or oxo group of donors; EC 1.3 includes oxidoreductases that act on the CH-CH group of donors (CH-CH oxidoreductases); EC 1.4 includes oxidoreductases that act on the CH-NH2 group of donors (Amino acid oxidoreductases, Monoamine oxidase); EC 1.5 includes oxidoreductases that act on CH-NH group of donors; EC 1.6 includes oxidoreductases that act on NADH or NADPH; EC 1.7 includes oxidoreductases that act on other nitrogenous compounds as donors; EC 1.8 includes oxidoreductases that act on a sulfur group of donors; EC 1.9 includes oxidoreductases that act on a heme group of donors; EC 1.10 includes oxidoreductases that act on diphenols and related substances as donors; EC 1.11 includes oxidoreductases that act on peroxide as an acceptor (peroxidases); EC 1.12 includes oxidoreductases that act on hydrogen as donors; EC 1.13 includes oxidoreductases that act on single donors with incorporation of molecular oxygen (oxygenases); EC 1.14 includes oxidoreductases that act on paired donors with incorporation of molecular oxygen; EC 1.15 includes oxidoreductases that act on superoxide radicals as acceptors; EC 1.16 includes oxidoreductases that oxidize metal ions; EC 1.17 includes oxidoreductases that act on CH or CH2 groups; EC 1.18 includes oxidoreductases that act on iron-sulfur proteins as donors; EC 1.19 includes oxidoreductases that act on reduced flavodoxin as a donor; EC 1.20 includes oxidoreductases that act on phosphorus or arsenic in donors; EC 1.21 includes oxidoreductases that act on X-H and Y-H to form an X-Y bond; and EC 1.97 includes other oxidoreductases.

  • The Energetics of Chemolithotrophy

    • Chemolithotrophs use electron donors oxidized in the cell, and channel electrons into respiratory chains, producing ATP.
    • Chemotrophs are organisms that obtain energy through the oxidation of electron donors in their environments.
    • In chemolithotrophs, the compounds - the electron donors - are oxidized in the cell, and the electrons are channeled into respiratory chains, ultimately producing ATP.
    • The electron acceptor can be oxygen (in aerobic bacteria), but a variety of other electron acceptors, organic and inorganic, are also used by various species.

  • Syntrophy and Methanogenesis

    • In methanogenesis, carbon is used as the terminal electron receptor instead of oxygen.
    • Although there are a variety of potential carbon based compounds that are used as electron receptors, the two best described pathways involve the use of carbon dioxide and acetic acid as terminal electron acceptors.
    • Only methanogenesis and fermentation can occur in the absence of electron acceptors other than carbon.