Final answer:
The extent to which reactants are converted into products spontaneously in a biochemical reaction is expressed as the free energy change (ΔG). The reaction will spontaneously proceed towards equilibrium if the free energy of the products is lower than that of the reactants.
Step-by-step explanation:
In a biochemical reaction, reactants may be converted into products. The extent to which this occurs spontaneously is expressed as the free energy change (ΔG) of the reaction. If the standard free energy of the products is smaller than that of the reactants, the reaction will take place spontaneously, moving towards equilibrium.
However, the actual extent of the reaction is influenced by several factors, including reaction conditions, the presence of a catalyst, the concentration of reactants and products, and the temperature.
In the case where reactants and products occupy a single phase, the idea of spontaneity implies that the equilibrium composition is achieved when the extent of reaction is between 0.5 and unity.
The free energy change also indicates the direction and extent of a reaction. When a system is not at equilibrium (‡ Q < K), the reaction moves spontaneously in the direction that will establish equilibrium, hence minimizing the system's free energy.