Electron transfer in the mitochondrial respiratory chain may...

Electron transfer in the mitochondrial respiratory chain may be represented by the net reaction equation $$\mathrm{NADH}+\mathrm{H}^{+}+\frac{1}{2} \mathrm{O}_{2} \rightleftharpoons \mathrm{H}_{2} \mathrm{O}+\mathrm{NAD}^{+}$$ (a) Calculate $\Delta E^{\prime \circ}$ for the net reaction of mitochondrial electron transfer. Use $E^{\prime \circ}$ values in Table 13-7. (b) Calculate $\Delta G^{\prime \circ}$ for this reaction. (c) How many ATP molecules can theoretically be generated by this reaction if the free energy of ATP synthesis under cellular conditions is $52 \mathrm{kJ} / \mathrm{mol} ?$

Electron transfer in the mitochondrial respiratory chain may be represented by the net reaction equation $$\mathrm{NADH}+\mathrm{H}^{+}+\frac{1}{2} \mathrm{O}_{2} \rightleftharpoons \mathrm{H}_{2} \mathrm{O}+\mathrm{NAD}^{+}$$
(a) Calculate $\Delta E^{\prime \circ}$ for the net reaction of mitochondrial electron transfer. Use $E^{\prime \circ}$ values in Table 13-7.
(b) Calculate $\Delta G^{\prime \circ}$ for this reaction.
(c) How many ATP molecules can theoretically be generated by this reaction if the free energy of ATP synthesis under cellular conditions is $52 \mathrm{kJ} / \mathrm{mol} ?$

Key Concepts

Standard Reduction Potentials

This concept involves the use of tabulated standard reduction potentials (E'° values) to gauge the propensity for different chemical species to gain or lose electrons. They are central to calculating the overall electromotive force (?E'°) of a redox reaction by comparing the potentials of the oxidized and reduced forms.

Gibbs Free Energy Change in Redox Reactions

The relationship ?G'° = ?nF?E'° connects the electrical work available from the reaction (?E'°) with the thermodynamic spontaneity via the change in Gibbs free energy (?G'°). This conversion is crucial for understanding how much energy is released by redox reactions under standard conditions.

Electron Transfer Stoichiometry

Correctly determining the number of electrons (n) transferred in the redox reaction is essential because it directly influences the calculation of both ?E'° and ?G'°. The stoichiometry of electron transfer defines how energy is partitioned among the participating species.

Mitochondrial Electron Transport Chain

This is the series of protein complexes and electron carriers in the mitochondrion that transfer electrons from donors like NADH to acceptors such as oxygen, leading to the formation of water. It is a fundamental process in cellular respiration and energy production.

ATP Synthesis Coupling

This concept describes how the free energy released from redox reactions, as quantified by ?G'°, is harnessed to drive the synthesis of ATP. The number of ATP molecules generated is determined by dividing the total free energy release by the free energy required to synthesize one ATP molecule, linking chemical energy conversion to cellular bioenergetics.

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