Which of the following regarding the ETC in the mitochondria is TRUE? A) Complex

Question

Which of the following regarding the ETC in the mitochondria is TRUE? A) Complex II receives electrons from NADH or FADH2 while Complex IV receives its electrons from Complex III. B) There is an increase in both the free energy and the electronegativity as electrons move through the protein complexes. C) The movement of electrons allows all four protein complexes to pump protons out of the matrix and into the intermembrane space. D) The proton motive force generated by the protein complexes is required for all ATP production that occurs within the mitochondria. E) There are no true statements above.

Explanation / Answer

Answer 9.(D)

(A) FALSE .Complex II of mitochondria receives electron from FADH2 and transfers it to ubiquinone (Q) which is a lipid soluble molecule. Ubiquinone receives electrons from both complex I and II and transfers it to complex III. Complex III then transfers electron through membrane to cytochrome c. Cytochrome c then transfers electron to molecular oxygen , reducing to water.

(B) FALSE. The Gibbs free energy is the available free energy to do work. So any reaction that decreases the overall Gibbs free energy of a system is a spontaneous reaction. As the electrons are transferred to the more electronegative acceptor in ETC, there is increase in electronegativity. With the increase in electronegativity of the complexes, free energy is released and the electrons finally attain a stability. Therefore there is decrease in free energy but increase in electronegativity.

(C) FALSE. Complex II does not transport hydrogen ion out of the matrix into the intermembrane space.

(D) TRUE Proton motive force generated by protein complexes is required for all ATP productioin that occurs within the mitochondria.

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