Lipid peroxidation

Lipid peroxidation is the oxidative degradation of lipids, endogenously, or in cooking. When radicals react with non-radicals, this always creates another radical. When a fatty acid reacts with a radical, a fatty acid-radical is created. This fatty acid-radical may react with oxygen to form a peroxyl-fatty acid radical. This peroxyl-fatty acid radical may react with another free fatty acid, producing two compounds: another fatty acid radical and a lipid peroxide. When such a radical chain reaction occurs inside a cell, it may cause death of this cell, as the cell membrane contains many lipids. This cycle is ended by an anti-oxidant, or (if there are lots of radicals) by another radical, because when two radicals react, they produce a non-radical. Anti-oxidants end a radical chain reaction by getting oxidized themselves (not rendering another radical).

Susceptibility to oxidation

Polyunsaturated fatty acids are more susceptible to lipoxidation than other fatty acids because they contain multiple carbon units with double bonds. The carbon unit in between two double-bonded carbon units is called a methylene bridge. This carbon unit has less energy invested in its bonds with the two hydrogen atoms, which makes these hydrogens more reactive.