What event will most likely occur if Protein X is inserted into the inner membrane of mitochondria?

• A. A. The citric acid cycle will cease to function.
• B. B. The electron transport chain will cease to function.
• C. C. The proton gradient across the inner membrane will dissipate.
• D. D. The pH of the intermembrane space will decrease.

Answer: (C)

When Protein X is inserted into the inner membrane of mitochondria, the most likely outcome is that the proton gradient across the inner membrane will dissipate. This is important because the inner mitochondrial membrane is vital for the function of the electron transport chain (ETC), which relies on the production of a proton gradient to drive ATP synthesis.

The ETC pumps protons from the mitochondrial matrix into the intermembrane space, creating a proton gradient. If Protein X disrupts the integrity of this membrane or provides an alternative pathway for protons to leak back into the matrix, the established gradient will collapse. This dissipation of the gradient directly impacts ATP synthesis and overall mitochondrial function, as the energy stored in the proton gradient is what drives ATP synthase to convert ADP and inorganic phosphate into ATP.

Therefore, the correct answer emphasizes the critical role of the proton gradient in cellular respiration and energy production within mitochondria.