The Fenton reaction leads to free radical generation when:

Ans. is 'c' i.e. Ferrous ions are converted to ferric ions Free radicals are generated through Fenton's reaction.In this reaction iron is converted from its ferrous to ferric form and a free radical is generated, i.e.(H2O+Fe2+ - Fe3++OH++OH-)Note H2O2 can also react with copper instead of iron to produce free radicals.Something about Free radicals:Free radicals are chemical species that have a single unpaired electron in the outer orbit.They are highly unstable particles. The excess energy due to this unstable configuration is released through chemical reactions with adjacent molecules such as proteins, lipids or carbohydrates, particularly with key molecules in membranes and nucleic acids. This causes membrane damage.* Antioxidant MechanismsThere are several enzymatic and non-enzymatic systems that terminate or inactivate the free radicals.Enzymatic systemsGlutathione peroxidase*Catalase*Super oxide dismutase*Non-enzymatic systemsVitamin E*Vitamin C*Sulfhydryl containing compoundscystine*glutathione*Serum proteinAlbumin*Ceruloplasmin*Transferrin*