Superoxide and hydroxyl radicals can be found in both cell components. Hydrogen peroxide is converted to water by the enzyme GSHpx. Those two enzymes effectively control most free radicals within the cytosol. Fatty acid radicals then react with other fatty acids producing a chain reaction. Vitamin E and to a lesser extent 3-carotene reacts with fatty acid radicals and stops the chain reaction.
Free radicals are highly reactive compounds because they are missing an electron.
Free radicals can react with nucleic acids causing mutations, they can react with enzymes and render them inactive, and they can react with fatty acids in membranes causing membrane instability .Free radicals can eventually kill cells and damage tissues.