In: Biology
A pH gradient exists between the internal and external surfaces of the inner mitochondrial membrane of 1.4 pH units, where the external side is more acidic.
a. If the membrane potential is 0.6 V (where the internal side is negative), what is the free energy change on transporting 1 mol of protons across the membrane from outside to inside at 298 K?
b. Under standard state conditions, how many protons must be transported to provide enough free energy for the synthesis of 1 mol of ATP?
a)
Gradient driven by pH difference and membrane potential difference
F = Faraday’s constant =96485
Δ ψ= membrane potential difference=-0.6 V
R=8.315 J / mol
T=298k
ΔpH=-1.4
= (96485X-0.6) + (2.303X 8.315X 298X-1.4)
= -65880 J/mol or -65.9 KJ/mol
b. For the synthesis of 1 ATPmolecule, 3 protons are required. Then for the synthesis of 1 mol of ATP, which contains 6.023X1023 ATP moleucles, 3 X6.023X1023 protons will be required= 1.8X1024 protons.