This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ETC, Subject name: Biochemistry
MELAS inhibit all ETC Complexes EXCEPT: 
Select and explain. 
A. I, B. II, C. III, D. IV
B: II
Answer: B: II 
Explanation: MELAS (mitochondrial encephalopathy, lactic acidosis, and stroke) MELAS inhibits complex I, III & IV of ETC. It is an inherited condition due to NADH-Q oxidoreductase, Caused by a mutation in mitochondrial DNA Involved in Alzheimer disease and diabetes mellitus. ETC is affected, brain is affected and due to anaerobic metabolism, lactic acidosis occurs.