This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Biochemistry
Which of the following is not involved in generation of proton gradient? 
Select and explain. 
A. NADPH dehydrogenase, B. Coenzyme Q cytoreductase, C. Succinate CoQ reductase, D. Cytochrome reductase
C: Succinate CoQ reductase
Answer: C: Succinate CoQ reductase 
Explanation: Proton gradient : The inner mitochondrial membrane, as such, is impermeable to protons (H+) and hydroxyl ions (OH-). The transpo of electrons through ETC is coupled with the. translocation of protons (H+) across the inner mitochondrial membrane (coupling membrane) from the matrix to the intermembrane space. The pumping of protons results in an electrochemical . or proton gradient. This is due to the. accumulation of more H+ ions (low pH) on the outer side of the inner mitochondrial membrane than the inner side. The proton . gradient developed due to the electron flow in the respiratory chain is sufficient to result in the synthesis of ATP from ADP and Pi. Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 229