Calculate Proton Motive Force (PMF)

The proton motive force is the combination of proton and voltage gradients across a membrane. The proton gradient is the difference in the concentration of protons on each side of the membrane.

To find out the proton concentration we use the formula:

pH = -log H+

Suppose, pH outside the membrane is 6.3. by Substituting it in the formula:

6.3 = -log H+

log 6.3 = H+

0.79 = H+

and pH inside the membrane is 7.2 ,Substituting in the formula:

7.2 = -log H+

log 7.2 = H+

0.85 = H+

The difference in proton concentrations is 0.85 - 0.79 = 0.06.

So, We add the membrane potential (i.e 0.018) to this value,

0.06 + 0.018 = 0.078.

This is the PMF = 0.078