This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
Lipid peroxidation in cells exposed to ionizing radiation is initiated by 
Select and explain. 
A. Catalase, B. Superoxide, C. Hydroxyl Radical, D. Glutathione
C: Hydroxyl Radical
Answer: C: Hydroxyl Radical 
Explanation: Radiolysis of water leads to formation of hydroxyl radicals that initiate lipid peroxidation of membrane phospholipids.