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
Cytochrome oxidase contains which of the following? 
Select and explain. 
A. Fe, B. Cu, C. Both of the above, D. None of the above
C: Both of the above
Answer: C: Both of the above 
Explanation: Each monomer of cytochrome oxidase contains one molecule of heme, and one atom each of iron and copper. Cytochrome oxidase is located in the mitochondrial membrane and it provides energy for cell by coupling electron transpo through the cytochrome chain with the process of oxidative phosphorylation. It is the terminal oxidase in the respiratory oxidation system. As a terminal enzyme in the oxidative phosphorylation process cytochrome oxidase is essential in cellular metabolism. Severe copper deficiency result in decreased cytochrome oxidase activity. Ref: Handbook on Metals in Clinical and Analytical Chemistry edited by Hans Gottlob Seiler, page 342.