Answer: 1.922x10⁻²⁰ Joules
Explanation: <u>Electric</u> <u>Potential</u> <u>Energy</u> (U) is the energy a charged object has due to its location in an electric field and it will only exist with the object is charged.
<u>Voltage</u> or <u>Electric</u> <u>Potential</u> <u>Difference</u> (V) is external work done to move a charge from one point to another in a electric field.
These terms have a relationship, which is given by:
where
q is the charge
Proton is positive and has a charge of 1.6x10⁻¹⁹C.
Unit for potential energy is Joule (J). The relation between mV and J is
1mV = 10⁻³J
Then:
V = 120x10⁻³
V = 0.12
So, for a proton to move from the negative side of a membrane to the positive:
= 1.922 x 10⁻²⁰
Energy necessary to transport a proton from negative side of the membrane to the positive is 1.922 x 10⁻²⁰J.