Now, if we take this and we basically represent this term as delta G, then this is the more common equation that you're used to seeing. So this quantity is actually Gibbs free energy. So the negative T multiplied by delta S of the universe is called Gibbs free energy. It has the units of Joules, and it is represented by delta G. So in equation four, if we rewrite this term with delta G, we basically get equation five. And this is the equation that gives us the Gibbs free energy when a process takes place. Now, if we look at equation three and we look at equation one, so we know from the second law of thermodynamics that in any real biological process, the change in entropy of the universe must always be a positive value.