For the problem in Sample Calculation 10-1, calculate ΔG at...

For the problem in Sample Calculation $10-1,$ calculate $\Delta G$ at $37^{\circ} \mathrm{C}$ when the membrane potential is (a) $-50 \mathrm{mV}$ (cytosol negative) and (b) $+150 \mathrm{mV}$. In which case is $\mathrm{Ca}^{2+}$ movement in the indicated direction thermodynamically favorable?

Key Concepts

Free_Energy_Change

This concept pertains to the calculation of the work associated with the transfer of species from one region to another. In the context of ion transport, the free energy change (?G) includes contributions from both the concentration (chemical) gradient and the electrical potential difference. The overall ?G helps determine whether a process is spontaneous, with negative values indicating thermodynamically favorable processes.

Membrane_Potential

Membrane potential is the electrical potential difference across a cell membrane resulting from the uneven distribution of ions. It plays a critical role in determining the energy required for ion movement across the membrane by influencing the electrical component of the electrochemical gradient.

Electrochemical_Gradient

The electrochemical gradient combines both the chemical gradient (difference in ion concentrations) and the electrical gradient (membrane potential) into a single driving force for ion movement. This comprehensive force determines the direction and magnitude of ion flux across membranes.

Thermodynamic_Favorability

Thermodynamic favorability refers to the likelihood that a process will occur spontaneously, with the defining criterion being a negative free energy change (?G < 0). In the context of ion transport, if the net driving force provided by the electrochemical gradient results in a negative ?G, the movement of ions in the specified direction is considered thermodynamically favorable.

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