Question

Question: Write a balanced equation for the oxidation of ubiquinol by cytochrome c. Calculate$∆$G$°$^$¢$ and$∆E$$°$^$¢$ for the reaction.

Short answer

The balanced equation is:

2 Cyto c (Fe³⁺) + ubiquinol $\to$2 cyroc ( Fe²⁺) + ubiquinone + 2H⁺

^{$∆E°=0.190V$}

$∆G°=-36.7kJ$mol^-1

Step-by-step solution

Definition of oxidation

Oxidation is the process of a molecule, an atom, or an ion losing electrons.

Balanced equation for oxidation

Ubiquinol is oxidized by cytochrome c(Fe³⁺), since cytochrome c (Fe³⁺) has higher reduction potential. Oxidation of ubiquinol releases 2 electrons, while cytochrome c(Fe³⁺) can only take 1, so 2 cytochromes c (Fe³⁺) are needed.

Thus, the balanced equation is:

2 cyto c (Fe³⁺) + ubiquinol $\to$2 cyto (Fe²⁺) + ubiquinone +2H⁺

Calculation of ΔG°’ and ΔE°’

$∆G°$' is calculated from$∆E°$change. All the data is obtained from the Table 14.4.

$$\begin{gathered} ∆E=E°Eelectronaceeptor)-E°(electrondonor) \\ =0.235V-0.045V \\ =0.190V \\ Now, \\ ∆G°=-nF∆E° \end{gathered}$$

= -2$\times$96.485 kJV^-1 mol^-1$\times$0.190 V

= -36.7kJ mol^-1