Atpenins are succinate-ubiquinone reductase inhibitors with antifungal properties. Atpenins illustrate the fact that:

Question

Atpenins are succinate-ubiquinone reductase inhibitors with antifungal properties.  Atpenins illustrate the fact that:

Quizplus · Accepted Answer

11ecba2d_0e39_8cd0_a3bf_a3b01283939e_MD0008_00 Succinate-ubiquinone reductase, also known as Complex II or succinate dehydrogenase, is an oxidoreductase found in the inner membrane of the mitochondria in eukaryotes. In the electron transport chain, Complex II facilitates the transport of electrons from succinate in the citric acid cycle to Complex III. Electrons move through Complex II by three consecutive reactions. First, electrons from succinate are transferred to flavin adenine dinucleotide (FAD) to produce FADH₂ as succinate is oxidized to fumarate. Then, FADH₂ is reoxidized to FAD when electrons are shuttled to the iron-sulfur centers in Complex II. Finally, a small mobile electron carrier called ubiquinone, or coenzyme Q, accepts electrons from the iron-sulfur centers and transports them to Complex III. Electrons transferred by Complex II contribute to the overall production of ATP, which provides cells with the energy to grow. The question indicates that atpenins are effective antifungal agents that inhibit succinate-ubiquinone reductase (ie, Complex II). Consequently, the correct answer choice should illustrate that atpenins disrupt at least one of the three reactions of Complex II. The transfer of electrons from Complex II to III through ubiquinone is the only reaction accurately described. (Choices A and B) Complexes I, III, and IV pump protons into the intermembrane space against their concentration gradient, but Complex II does not pump protons against their gradient, and therefore does not contribute to the decrease in pH in the intermembrane space. (Choice D) In the electron transport chain, electrons are transferred to carriers with higher redox potentials at each step. Electrons are transferred from ubiquinone to cytochrome c reductase (Complex III) because ubiquinone has a lower, not a higher, redox potential. Educational objective: Complex II (succinate-ubiquinone reductase or succinate dehydrogenase) oxidizes succinate to fumarate and transfers electrons to Complex III. Electrons are transferred from flavin adenine dinucleotide (FAD) to iron-sulfur centers in Complex II, then to ubiquinone (coenzyme Q), which carries them to Complex III through the inner membrane.

Atpenins Are Succinate-Ubiquinone Reductase Inhibitors with Antifungal Properties