Question

In the liver mitochondria, the membrane potential is -0.17 V (negative inside). The pH difference is -0.5 (pHoutside – pHinside). The charge on a proton is (+1). What is the proton motive force (the amount of energy stored in the gradient)?

The Gibbs free energy for the gradient is [96485 X -.17] + [2.303 X 8. 315 X 310 X -0.5] = -19.4 kJ/mol.

Please explain the formula and what is the question asking for, Thank you.

Answer 1

The question is asking for proton motive force

∆G = nF∆psi - 2.303nRT ∆pH

∆ psi = membrane potential = -0.17 , n = 1

F = 96485 , R = 8.313 (gas constant) , T (temp in kelvi ) = 310K

Here we have to calculate the amount of energy stored in the gradient

So , ∆G = (96458 × - .17) + ( 2.303 × 8.315 × 310 × -0.5)

= -19.36 KJ/mol.