All are free radicals except: (A) Superoxide, (B) Hydrogen peroxide, (C) peroxyl, (D) Hydroperoxyl
Answer is B. Hydrogen peroxide is a reactive oxygen species but not a free radical because all electrons are paired. Clinical correlate: Chronic granulomatous disease also knows as Bridges-Good syndrome is due to deficiency of NADPH oxidase. The lysosomes are unable to produce hydrogen peroxide to kill the bacteria. The patients have increased susceptibility towards catalase-positive organisms. Reference: Harpers illustrated biochemistry 30th edition