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
Which complex in mitochondrial ETC does not pump out H ions ? 
Select and explain. 
A. Complex I, B. Complex II, C. Complex III, D. Complex IV
B: Complex II
Answer: B: Complex II 
Explanation: Complex II Complex II does not act as proton (H+) pump.Complex I: NADH CoQ-reductase Permit ATP formation (Site I) Act as proton pumpComplex II: Succinate Co() rcductase No ATP formComplex CoQ - cytochrome - C reductase Permit ATP formation (Site II) Act as proton pumComplex IV: Cytochrome C oxidase Permit ATP formation (Site III) Act as proton pump