Question

What is Gibbs energy and Energy coupling? Are they related if so how?

Answer 1

Gibbs energy (G) is the energy associated with a chemical reaction that can be further used to do work.
G = H – T x S
H – enthalpy (joule) – it is the total heat / energy produced in a thermodynamic system at a constant pressure
T – temperature (kelvin)
S – entropy (joule/kelvin) – it is the change of energy in a chemical reaction
Or
G = U + PV – TS
U – internal energy (joule)
P – Pressure (Pascal)
V – volume (m3)
T – temperature (kelvin)
S – entropy (joule/kelvin)

Energy coupling basically represents the relation between chemical reactions. The energy produced by one reaction is utilized by the other reaction.
We will able to understand their similarity by citing a simple example,
In our body, catabolic reactions breaks the energy source to produce ATP from ADP, which is further used to undergo anabolic reactions. (See the attached figure)

Just like this, Gibbs energy also uses the energy produced by the initial reaction to carry on the upcoming chemical reaction.