This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Xanthine Oxidase is associated with which co-factor: \nSelect and explain. \nA. Zinc, B. Copper, C. Selenium, D. Molybdenum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Glutathione peroxidase contains selenium.Xanthine oxidase is large protein, having a molecular weight of 270,000, and has 2 flavin molecules (bound as FAD), 2 molybdenum atoms and 8 iron atoms bound per enzymatic unit.The molybdenum atoms are contained as molybdopterin cofactors and are the active sites of the enzyme.The iron atoms are pa of (2Fe-2S) ferredoxin iron-sulfur clusters and paicipate in electron transfer reactions', 'role': 'assistant'}]