Hydrogen Cyanide is a lethal gaseous poison. Sodium and Potassium Cyanide are lethal solid poisons. Cyanide ions, which are produced when cyanide is dissolved in water, work as a poison by disabling a cell's ability to use oxygen, essentially suffocating the cell. When inhaled or ingested, the cyanide ions inhibit the enzyme cytochrome c oxidase in the mitochondria of an organism's cells, interfering with aerobic respiration and preventing the cells from generating energy. Cyanide poisoning especially affects the nervous system and cardiovascular system because they are so metabolically active and highly dependent on aerobic respiration. It has been speculated that cyanide poisoning feels like having one's face completely encased in plastic wrap and suffocating.