Question

Does this cycle of reactions appear in nature?

Answer 1

Does anyone know a real-world example of a cycle exactly like this:



or in other words, this:

A+C1⟶C2X+C2⟶C3C3⟶B+C4C4⟶Y+C1A+CX1⟶CX2X+CX2⟶CX3CX3⟶B+CX4CX4⟶Y+CX1

where the reaction A⟶BA⟶B is exergonic (i.e., involves a decrease in free energy) while X⟶YX⟶Yis endergonic (i.e., involves a free energy increase)?

The idea is that the above cycle, presumably catalyzed so that all the reactions go fairly fast under normal conditions, 'couples' the exergonic reaction to the endergonic reaction, thus driving the endergonic one.