Question

For a particular cell at 25°C, the concentration of sucrose is 10 mM on the inside of the cell and 0.5 mM on the outside, whereas the concentration of sodium ions (Na+) is 0.5 mM on the inside of the cell and 10 mM on the outside. The membrane potential is -150 mV.

Constants: R = 1.987 cal/mol-K; T = 25°C = 298 K; F = 23,062 cal/mole-volt
What would be the net ∆G for the coupling of these two reactions?
A) +7.007 kcal/mol
B) +3.459 kcal/mol
C) −1.774 kcal/mol
D) −3.459 kcal/mol
E) −7.007 kcal/mol

Answer 1

The net ∆G for the coupling of these two reactions is approximately -6.92 kcal/mol.

Step-by-step explanation:

The net ΔG for the coupling of these two reactions can be calculated using the Nernst equation:

ΔG = -nFΔE

Where ΔG is the net Gibbs free energy change, n is the number of moles of electrons transferred, F is the Faraday constant, and ΔE is the cell potential.

In this case, the two reactions being coupled are the movement of sucrose and sodium ions across the cell membrane. The number of moles of electrons transferred is 0, since no electron transfer is involved.

Using the given values, the net ΔG can be calculated as:

ΔG = - (2)(23,062 cal/(mol-V))(0.15 V) = -6,918.6 cal/mol ≈ -6.92 kcal/mol

Therefore, the net ΔG for the coupling of these two reactions is approximately -6.92 kcal/mol.