Question

1. Which complex in the electron transport chain does not contribute to the proton gradient across the mitochondrial membrane?
   
   A. Complex I
   B. Complex IV
   C. Complex II
   D. Complex III
2. Which statement regarding the mitochondrial electron transport chain and oxidative phosphorylation is true?
   
   A. Ubiquinone and the F zero subunit of ATP synthase are peripheral membrane proteins.
   B. Complexes I, II, III, and IV all are proton pumps.
   C. The final electron acceptor is water.
   D. Complex II is considered part of the electron transport chain, but also catalyzes a reaction in the TCA cycle.
   E. Complex III is exceptional in that it can synthesize ATP by itself.
3. Which of the following ordered sequences of the various components of the electron transport chain and oxidative phosphorylation will effectively allow the development of an electrochemical potential sufficient to drive the generation of high energy phosphate bonds between ADP and Pi?
   
   A. succinate dehydrogenase/FAD₂H complex, Coenzyme Q, cytochrome b-c1, cytochrome c, cytochrome a1-a3, F1F0-ATPase
   B. Complex I, Complex III, ubiquinone, cytochrome a-a3, cytochrome c, Complex IV, Complex V
   C. cytochrome oxidase, NADH dehydrogenase, CoQ, cytochrome b-c1, cytochrome c, ATP synthase
   D. FMN, NADH dehydrogenase, ubiquinone, cytochrome c, cytochrome oxidase, F1F0- ATPase
   E. NADH dehydrogenase, CoQ, cytochrome c, cytochrome oxidase, cytochrome b-c1, F1F0-ATPase

4. Which of the following statements about oxidative phosphorylation in mitochondria is incorrect?
   
   A. Extrusion of H⁺ from the matrix accompanies electron transport.
   B. Addition of ADP stimulates oxygen consumption.
   C. Submitochondrial fragments show no ATP synthase activity.
   D. The ATP-ADP exchange mechanism decreases the membrane potential.
   E. Addition of thyroxin increases the P/O ratio.

Answer 1

1) Answer : C. Complex II

succinate dehydrogenase or complex II does not contribute to proton transport across inner mitochondrial membrane to inter membrane space.

2) Answer : D. Complex II is considered part of the electron transport chain, but also catalyzes a reaction in the TCA cycle.

Ubiquinone and the F zero subunit of ATP synthase integral membrane proteins. Complex II is not a proton pump. The final electron acceptor is oxygen. Only ATP synthase can synthesize ATP by chemi-osmotic mechanism