Question

Many types of cellular metabolic reactions at constant temperature and pressure are known to exhibit oscillations, in which the concentration of a given metabolite constantly changes but does not ever reach a steady-state, equilibrium value. We know that any set of chemical reactions will proceed while the free energy decreases. But in an oscillatory cycle, the change in free energy must be zero. How do you resolve this paradox?

Answer 1

Undoubtedly, the total free energy change during a metabolic or chemical reaction decreases as the reaction proceeds. However, the biological reactions have a slight difference as compared to chemical reactions. Biological metabolic reactions are a combination of anabolic and catabolic reactions. This states that the amount of energy required to generate a product sometimes equals to the amount of energy required to degrade a substrate, thus leading to a cyclic process containing oscillating reactions. Under such conditions, the net free energy change comes out to be zero but the reaction still proceeds usually.

Hence, the paradox can be solved and understood in the terms of anabolic and catabolic reactions unlike chemical reactions.