Anaerobic respirationAnaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain. In aerobic organisms undergoing respiration, electrons are shuttled to an electron transport chain, and the final electron acceptor is oxygen. Molecular oxygen is an excellent electron acceptor. Anaerobes instead use less-oxidizing substances such as nitrate (NO3-), fumarate (C4H2O42-), sulfate (SO42-), or elemental sulfur (S).
Reaction rateThe reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. Reaction rates can vary dramatically. For example, the oxidative rusting of iron under Earth's atmosphere is a slow reaction that can take many years, but the combustion of cellulose in a fire is a reaction that takes place in fractions of a second.
Electron transport chainAn electron transport chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. The electrons that are transferred from NADH and FADH2 to the ETC involves four multi-subunit large enzymes complexes and two mobile electron carriers.
HydrogeologyHydrogeology (hydro- meaning water, and -geology meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquifers). The terms groundwater hydrology, geohydrology, and hydrogeology are often used interchangeably. Hydrogeology is the study of the laws governing the movement of subterranean water, the mechanical, chemical, and thermal interaction of this water with the porous solid, and the transport of energy, chemical constituents, and particulate matter by flow (Domenico and Schwartz, 1998).
Aerobic organismAn aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. The ability to exhibit aerobic respiration may yield benefits to the aerobic organism, as aerobic respiration yields more energy than anaerobic respiration. Energy production of the cell involves the synthesis of ATP by an enzyme called ATP synthase. In aerobic respiration, ATP synthase is coupled with an electron transport chain in which oxygen acts as a terminal electron acceptor.
Sulfur cycleThe sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes.
SulfateThe sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many are prepared from that acid. "Sulfate" is the spelling recommended by IUPAC, but "sulphate" was traditionally used in British English. The sulfate anion consists of a central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement.
TrichloroethyleneTrichloroethylene (TCE) is a halocarbon with the formula C2HCl3, commonly used as an industrial degreasing solvent. It is a clear, colourless non-flammable liquid with a chloroform-like sweet smell. The IUPAC name is trichloroethene. Industrial abbreviations include TCE, trichlor, Trike, Tricky and tri. It should not be confused with the similar 1,1,1-trichloroethane, which is commonly known as chlorothene. It has been sold under a variety of trade names.
BenzeneBenzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon.
RedoxRedox (ˈrɛdɒks , ˈriːdɒks , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: Electron-transfer – Only one (usually) electron flows from the atom being oxidized to the atom that is reduced. This type of redox reaction is often discussed in terms of redox couples and electrode potentials.
Sulfur assimilationSulfur assimilation is the process by which living organisms incorporate sulfur into their biological molecules. In plants, sulfate is absorbed by the roots and then be transported to the chloroplasts by the transipration stream where the sulfur are reduced to sulfide with the help of a series of enzymatic reactions. Furthermore, the reduced sulfur is incorporated into cysteine, an amino acid that is a precursor to many other sulfur-containing compounds.
DenitrificationDenitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter.
