Question

What is the ΔG°′ value for the portion of the citric acid cycle that converts malate and acetyl-CoA to citrate?

Short answer

The total value of$\Delta G^{o\text{'}}=-1.8 kJ mo{l}^{-1}$.

Step-by-step solution

Conversion of malate to citrate

Citrate is formed from malate by malate dehydrogenase and citrate synthase reactions.The conversion of $\text{malate}\to \text{citrate}$reactions and their values are as follows:

$Malate+NA{D}^{+}\to oxaloacetate+NADH+H^{+};△G°{\text{'}}_1=+29.7kJmol{e}^{-1}$

(Malate dehydrogenase reaction)

$Acetyl-CoA+oxaloacetate\to citrate;△G°{\text{'}}_2=-31.5kJmo{l}^{-1}$ (Citrate synthase reaction)

Total △G°'is the sum of △G°'values of malate dehydrogenase and citrate synthase reaction

Total $△G°\text{'}$for the conversion of malate to citrate is computed by adding the preceding values of $△G°{\text{'}}_1$and$△G°{\text{'}}_2$by the following formula:

Total

role="math" localid="1648637329656" $$\begin{gathered} △\mathrm{G}°\text{'}=△\mathrm{G}°{\text{'}}_1+△\mathrm{G}°{\text{'}}_2 \\ =+29.7{\mathrm{kJmol}}^{-1}+(-31.5{\mathrm{kJmol}}^{-1}) \\ =-1.8{\mathrm{kJmol}}^{-1} \end{gathered}$$

Therefore, the value of$△G°\text{'}$ is$-1.8{\mathrm{kJmol}}^{-1}$ .