Passage
Catabolism is an oxidative process in which electrons are transferred from lipids, proteins, and carbohydrates to generate high-energy electron carriers from nicotinamide adenine dinucleotide (NADH/NAD⁺) and flavin adenine dinucleotide (FADH₂/FAD) . Both are used in the electron transport chain (ETC) as electron providers in a series of reactions. The transfer of electrons provides energy that drives oxidative phosphorylation and the production of ATP. Reduction of NAD⁺ proceeds according to the following half-reaction:
Reaction 1Reactions in the ETC occur in four protein complexes (I-IV) located in the inner mitochondrial membrane. Here high-energy electrons are shuttled from complexes I, II, and III to complex IV, where O₂ serves as the final electron acceptor. The net result of NADH oxidation is described by Reaction 2.
NADH+H++12O2→NAD++H2OReaction 2At complexes I, III, and IV, hydrogen ions move from the mitochondrial matrix to the intermembrane space and create the electrochemical gradient, or proton motive force (pmf) , that drives ATP synthesis. Each NADH molecule drives the net pumping of 10 protons across the membrane, as per Reaction 3.
NADH+11H++12O2→NAD++10H++H2OReaction 3
Adapted from Garrett R, Grisham CM, Sabat M. Biochemistry. Cengage Learning; 2011.
-Which of the following is NOT true concerning catabolism and the function of the ETC?

Question

Passage
Catabolism is an oxidative process in which electrons are transferred from lipids, proteins, and carbohydrates to generate high-energy electron carriers from nicotinamide adenine dinucleotide (NADH/NAD⁺) and flavin adenine dinucleotide (FADH₂/FAD) . Both are used in the electron transport chain (ETC) as electron providers in a series of reactions. The transfer of electrons provides energy that drives oxidative phosphorylation and the production of ATP. Reduction of NAD⁺ proceeds according to the following half-reaction:

Reaction 1Reactions in the ETC occur in four protein complexes (I-IV) located in the inner mitochondrial membrane. Here high-energy electrons are shuttled from complexes I, II, and III to complex IV, where O₂ serves as the final electron acceptor. The net result of NADH oxidation is described by Reaction 2.

NADH+H++12O2→NAD++H2OReaction 2At complexes I, III, and IV, hydrogen ions move from the mitochondrial matrix to the intermembrane space and create the electrochemical gradient, or proton motive force (pmf) , that drives ATP synthesis. Each NADH molecule drives the net pumping of 10 protons across the membrane, as per Reaction 3.

NADH+11H++12O2→NAD++10H++H2OReaction 3
Adapted from Garrett R, Grisham CM, Sabat M. Biochemistry. Cengage Learning; 2011.
-Which of the following is NOT true concerning catabolism and the function of the ETC?

Quizplus · Accepted Answer

11ecba2d_11a0_376e_a3bf_9d3c5c2a4500_MD0008_00 Catabolism breaks down biological fuel molecules such as carbohydrates, lipids, and proteins, releasing energy as they are oxidized. Oxidation cannot occur without reduction, so some other molecule must be reduced in the process. NADH can be oxidized and therefore serves as a reducing agent. Furthermore, NADH is not required for catabolism. Instead, NAD⁺ serves as an oxidizing agent for catabolic reactions and is reduced to NADH in the process. NADH enters the ETC as a reducing agent after catabolic oxidation of fuel molecules and provides the energy for the production of ATP. The question asks which of the given statements is NOT true concerning catabolism and the function of the ETC. Therefore, Choice C is the correct answer because NADH does NOT serve as an oxidizing agent in catabolism. (Choice A) ATP production requires energy input, which is measured by ΔG. The number of ATP molecules that can be produced depends on the energy available. (Choice B) ΔG (Gibbs free energy) depends on ΔE (reduction potential) and is related by the Nernst equation: ΔG = −nF ΔE. (Choice D) NADH and FADH₂, which are produced by catabolic oxidation of lipids, proteins, and carbohydrates, provide energy for ATP production by passing high-energy electrons through the ETC. This process is also known as electron transduction. Educational objective: Catabolism is an oxidative process that releases energy. During catabolic oxidation of fuel molecules, oxidizing agents such as NAD⁺ are reduced. Electron transduction from these reduced cofactors provides the energy for ATP synthesis.

Passage Catabolism Is an Oxidative Process in Which Electrons Are Transferred