reactive oxygen species are produced in the body at blood homeostasis.
where are reactive oxygen species produced in the body?
blood homeostasis
in sea water, ros can be generated through abiotic as well as biotic processes, among which are the radiolysis and photolysis of water molecules and cellular respiration. according to a model proposed by fan for the prediction of ros in surface waters, the biochemistry mediated by phytoplankton may be just as important for the production of ros as photochemistry. biological ros is often synthesized in mitochondrial membranes, as well as the endoplasmic reticulum of animals, plants, and some bacteria. in addition, chloroplasts and the organelles peroxisomes and glyoxysomes are also sites for the generation of ros. the ros most likely released to the environment are those produced at the cell surface as electrons get "leaked" from the respiratory chain and react with molecular oxygen, o. the products of this subsequent reduction of molecular oxygen are what are referred to as reactive oxygen species. thus, the production of ros is in direct proportion to the concentration of o in the system, with increases of o leading to higher production of ros. there are three main reactive oxygen species: the superoxide anion (o), hydrogen peroxide (ho), and the hydroxyl radical (oh•). the superoxide anion is formed directly from the one-electron reduction of molecular oxygen. hydrogen peroxide is then formed from the disproportionation of the superoxide anion. this reaction occurs very quickly in seawater. next, the reduction of hydrogen peroxide yields the hydroxyl radical, ho↔2oh•, which can then get reduced to the hydroxyl ion and water. however, the presence of reactive oxygen species in marine systems is hard to detect and measure accurately, for a number of reasons. first, ros concentrations are generally low (nanomoles) in seawater. second, they may react with other hard to identify molecules that occur in low quantities, resulting in unknown products. finally, they are (for the most part) transient intermediates, having lifetimes as little as microseconds.
reactive oxygen species production in marine microalgae
arsenic can cause oxidative stress through the formation of reactive oxygen species (ros), and reactive nitrogen species (rns). reactive oxygen species are produced by the enzyme nadph oxidase, which transfers electrons from nadph to oxygen, synthesizing a superoxide, which is a reactive free radical. this superoxide can react to form hydrogen peroxide and a reactive oxygen species. the enzyme nadph oxidase is able to generate more reactive oxygen species in the presence of arsenic, due to the subunit p22phax, which is responsible for the electron transfer, being upregulated by arsenic. the reactive oxygen species are capable of stressing the endoplasmic reticulum, which increases the amount of the unfolded protein response signals. this leads to inflammation, cell proliferation, and eventually to cell death. another mechanism in which reactive oxygen species cause cell death would be through the cytoskeleton rearrangement, which affects the contractile proteins.
arsenic biochemistry