oxidation

(noun)

A reaction in which the atoms of an element lose electrons and the valence of the element increases.

Related Terms

Examples of oxidation in the following topics:

  • Nitrification

    • Nitrobacter plays an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil.
    • Nitrification is the net result of two distinct processes: oxidation of ammonium to nitrite (NO2−) by nitrosifying or ammonia-oxidizing bacteria and oxidation of nitrite (NO2−) to nitrate (NO3−) by the nitrite-oxidizing bacteria.
    • Nitrification is a process of nitrogen compound oxidation (effectively, loss of electrons from the nitrogen atom to the oxygen atoms):
    • Biochemically, ammonium oxidation occurs by the stepwise oxidation of ammonium to hydroxylamine (NH2OH) by the enzyme ammonium monooxygenase in the cytoplasm, followed by the oxidation of hydroxylamine to nitrite by the enzyme hydroxylamine oxidoreductase in the periplasm.
    • Oxygen is required in ammonium and nitrite oxidation, meaning that both nitrosifying and nitrite-oxidizing bacteria are aerobes.

  • Oxidation of Reduced Sulfur Compounds

    • Sulfur oxidation involves the oxidation of reduced sulfur compounds, inorganic sulfur, and thiosulfate to form sulfuric acid.
    • Sulfur oxidation involves the oxidation of reduced sulfur compounds such as sulfide (H2S), inorganic sulfur (S0), and thiosulfate (S2O2−3) to form sulfuric acid (H2SO4).
    • An example of a sulfur-oxidizing bacterium is Paracoccus.
    • In addition to aerobic sulfur oxidation, some organisms (e.g.
    • Marine autotrophic Beggiatoa species are able to oxidize intracellular sulfur to sulfate.

  • Microbial Ore Leaching

    • Bacteria perform the key reaction of regenerating the major ore oxidizer which in most cases is ferric iron as well as further ore oxidation.
    • (2)$4 \ Fe^{\,2+} + \ O_2 + 4 \ H^+ \longrightarrow 4 \ Fe^{\,3+} + 2 \ H_2O$ (iron oxidizers)
    • (3) $S_2O_3^{\,2-} + 2 \ O_2 + H_2O \longrightarrow 2 \ SO_4^{\,2-} + 2 \ H^+$ (sulfur oxidizers)
    • The microbial oxidation process occurs at the cell membrane of the bacteria.
    • The critical reaction is the oxidation of sulfide by ferric iron.

  • Lipid Metabolism

    • Biological lipids, which are broken down and utilized though β-oxidation, represent a potent energy source.
    • In brief, the oxidation of lipids proceeds as follows: two-carbon fragments are removed sequentially from the carboxyl end of the fatty acid after dehydrogenation, hydration, and oxidation to form a keto acid, which is then cleaved by thiolysis.
    • β-oxidation can be broken down into a series of discrete steps:
    • Oxidation: The initial step of β-oxidation is catalyzed by acyl-CoA dehydrogenase, which oxidizes the fatty acyl-CoA molecule to yield enoyl-CoA.
    • Cleavage: A thiolase then cleaves off acetyl-CoA from the oxidized molecule, which also yields an acyl-CoA that is two carbons shorter than the original molecule that entered the β-oxidation pathway.

  • Anoxic Hydrocarbon Oxidation

    • Anoxic hydrocarbon oxidation can be used to degrade toxic hydrocarbons, such as crude oil, in anaerobic environments.
    • Anaerobic oxidation of methane (AOM) is a microbial process that occurs in anoxic marine sediments.
    • It is estimated that almost 90% of all the methane that arises from marine sediments is oxidized anaerobically by this process.
    • Recent investigations have shown that some syntrophic pairings are able to oxidize methane with nitrate instead of sulfate.
    • Describe the process of anoxic hydrocarbon oxidation in regards to marine environments

  • Iron Oxidation

    • There are three distinct types of ferrous iron-oxidizing microbes.
    • These microbes oxidize iron in environments that have a very low pH and are important in acid mine drainage.
    • The second type of microbes oxidizes ferrous iron at cirum-neutral pH.
    • Biochemically, aerobic iron oxidation is a very energetically poor process which therefore requires large amounts of iron to be oxidized by the enzyme rusticyanin to facilitate the formation of proton motive force.
    • Outline the purpose of iron oxidation and the three types of ferrous iron-oxidizing microbes (acidophiles, microaerophiles and anaerobic photosynthetic bacteria)

  • Proton Reduction

    • Reduction occurs when an oxidant gains an electron.
    • The overall process of creating energy in this fashion is termed oxidative phosphorylation.
    • The electron acceptor NAD+ is regenerated from NADH formed in oxidative steps of the fermentation pathway by the reduction of oxidized compounds.
    • 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 every redox reaction you have two halves: reduction and oxidation.

  • Fermentation Without Substrate-Level Phosphorylation

    • Fermentation is the process of extracting energy from the oxidation of organic compounds such as carbohydrates.
    • Even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to oxidative phosphorylation, as long as sugars are readily available for consumption (a phenomenon known as the Crabtree effect).
    • Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound.
    • Fermentation is important in anaerobic conditions when there is no oxidative phosphorylation to maintain the production of ATP (adenosine triphosphate) by glycolysis.
    • For example, even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to oxidative phosphorylation, as long as sugars are readily available for consumption (a phenomenon known as the Crabtree effect).

  • The Pentose Phosphate Shunt

    • There are two distinct phases in the pathway: the oxidative phase and the non-oxidative phase .
    • The first is the oxidative phase in which glucose-6-phosphate is converted to ribulose-5-phosphate.
    • The second phase of this pathway is the non-oxidative synthesis of 5-carbon sugars.
    • Additionally, NADPH can be used by cells to prevent oxidative stress.
    • Outline the two major phases of the pentose phosphate shunt: oxidative and non-oxidative phases

  • Nitrate Reduction and Denitrification

    • Denitrification is a microbially facilitated process involving the stepwise reduction of nitrate to nitrite (NO2-) nitric oxide (NO), nitrous oxide (N2O), and, eventually, to dinitrogen (N2) by the enzymes nitrate reductase, nitrite reductase, nitric oxide reductase, and nitrous oxide reductase.
    • Protons are transported across the membrane by the initial NADH reductase, quinones and nitrous oxide reductase to produce the electrochemical gradient critical for respiration.
    • Complete denitrification is an environmentally significant process because some intermediates of denitrification (nitric oxide and nitrous oxide) are significant greenhouse gases that react with sunlight and ozone to produce nitric acid, a component of acid rain.
    • Other genes involved in denitrification include nir (nitrite reductase) and nos (nitrous oxide reductase), which are possessed by such organisms as Alcaligenes faecalis, Alcaligenes xylosoxidans, Pseudomonas spp, Bradyrhizobium japonicum, and Blastobacter denitrificans.