Potassium cyanide is a biologically active, rapidly acting, inorganic compound that is traditionally known as a poison. Potassium cyanide is a potent inhibitor of cellular respiration, acting on mitochondrial cytochrome c oxidase, hence blocking oxidative phosphorylation. This prevents the body from oxidizing food to produce useful energy. Exposure to potassium cyanide can be rapidly fatal. It has whole-body (systemic) effects, particularly affecting those organ systems most sensitive to low oxygen levels: the central nervous system, the cardiovascular system, and the pulmonary system. Potassium cyanide is used by professional entomologists as a killing agent in collecting jars, as insects succumb within seconds to the HCN fumes it emits, thereby minimizing damage to even highly fragile specimens. Potassium cyanide is also used commercially for fumigation, electroplating, and extracting gold and silver from ores.