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.
-Researchers want to measure the reduction potential when NADH is oxidized by oxygen to compare the experimental potential with the calculated reduction potential in the mitochondria. They set up a galvanic cell, as shown in the following diagram. Which of the following statements is true about NAD⁺/NADH in this experiment?

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.
-Researchers want to measure the reduction potential when NADH is oxidized by oxygen to compare the experimental potential with the calculated reduction potential in the mitochondria. They set up a galvanic cell, as shown in the following diagram.

Which of the following statements is true about NAD⁺/NADH in this experiment?

Quizplus · Accepted Answer

11ecba2d_119f_4d0c_a3bf_eda9e2de7884_MD0008_00 A galvanic cell (eg, a battery) is an electrochemical cell in which an electric potential is produced due to the spontaneous redox reaction that favors the movement of electrons. In any electrochemical cell, oxidation occurs at the anode and reduction occurs at the cathode as electrons flow from the anode to the cathode. The mnemonics "AN OX" and "RED CAT" may be helpful in remembering this association: anode and oxidation go together, and reduction and cathode go together. Because NADH is oxidized to NAD⁺, it must be at the anode and it must lose electrons. This process produces an electric potential as electrons spontaneously flow from anode to cathode. (Choice A) Although oxidation does occur at the anode, NAD⁺ is the product of NADH oxidation, and does not itself become oxidized. (Choice B) An electrical potential already exists because NADH spontaneously loses two electrons to form NAD⁺; no potential needs to be applied. Furthermore, the loss of electrons occurs at the anode rather than the cathode. (Choice C) Galvanic cells are composed of two half-cells, with one half containing the molecule that becomes oxidized at the anode (in this case, NADH) and the other half containing the molecule that becomes reduced at the cathode (in this case, O₂). NADH and NAD⁺ must be in the same half-cell because one is made from the other. Similarly, O₂ and H₂O₂ must be together in the other half-cell. Educational objective: Galvanic cells are electrochemical cells that produce an electric potential as a result of the spontaneous transfer of electrons from the anode to the cathode. In any electrochemical cell, oxidation occurs at the anode and reduction occurs at the cathode.

Passage Catabolism Is an Oxidative Process in Which Electrons Are Transferred