In a muscle, the extracellular and intracellular concentrations of ${Na^+}$ are $150 \text{ mM}$ and $12 \text{ mM}$, and those of ${K^+}$ are $2.7 \text{ mM}$ and $140 \text{ mM}$, respectively. Assume that the temperature is ${25^\circ C}$ and that the membrane potential is $-60 \text{ mV}$, with the interior more negatively charged than the exterior. ($R = 8.314 \text{ J} \text{ mol}^{-1} {K^{-1}}$; $F = 96.45 \text{ kJ} \text{ mol}^{-1} {v^{-1}}$)
The free energy change for the transport of three ${Na^+}$ out of the cell is
- $+1.5 \text{ kJ/mol}$
- $+17.4\text{ kJ/mol}$
- $+18.9 \text{ kJ/mol}$
- $+36.3 \text{ kJ/mol}$
