<P> The bombardier beetle has a device which allows it to shoot corrosive and foul - smelling bubbles at its enemies . The beetle produces and stores hydroquinone and hydrogen peroxide, in two separate reservoirs in the rear tip of its abdomen . When threatened, the beetle contracts muscles that force the two reactants through valved tubes into a mixing chamber containing water and a mixture of catalytic enzymes . When combined, the reactants undergo a violent exothermic chemical reaction, raising the temperature to near the boiling point of water . The boiling, foul - smelling liquid partially becomes a gas (flash evaporation) and is expelled through an outlet valve with a loud popping sound . </P> <P> Hydrogen peroxide is a signaling molecule of plant defense against pathogens . </P> <P> Hydrogen peroxide has roles as a signalling molecule in the regulation of a wide variety of biological processes . The compound is a major factor implicated in the free - radical theory of aging, based on how readily hydrogen peroxide can decompose into a hydroxyl radical and how superoxide radical byproducts of cellular metabolism can react with ambient water to form hydrogen peroxide . These hydroxyl radicals in turn readily react with and damage vital cellular components, especially those of the mitochondria . At least one study has also tried to link hydrogen peroxide production to cancer . These studies have frequently been quoted in fraudulent treatment claims . </P> <P> The amount of hydrogen peroxide in biological systems can be assayed using a fluorimetric assay . </P>

What is the oxidation number of o in h2o2