What factors determine whether a biochemical reaction will proceed spontaneously?

The spontaneity of a biochemical reaction is fundamentally determined by thermodynamic principles, particularly changes in free energy. A reaction is considered spontaneous if it occurs without the need for external energy input, which is often assessed through the Gibbs free energy change (ΔG) associated with the reaction.

When ΔG is negative, this indicates that the products of the reaction have a lower free energy than the reactants, thus the reaction can proceed spontaneously in the forward direction. In contrast, a positive ΔG would signify a non-spontaneous reaction under standard conditions. Therefore, thermodynamics, which encompasses the laws governing energy transformations and the relationship between heat and other forms of energy, plays a crucial role in determining the feasibility of a reaction.

Although factors such as the presence of substrates, activation energy, temperature, and enzyme concentration can influence the rate of reaction or the conditions under which a reaction may occur, they do not fundamentally dictate whether a reaction is spontaneous. For instance, while activation energy must be overcome for a reaction to proceed, it does not alter the basic thermodynamic favorability indicated by the ΔG. Similarly, changes in temperature can influence the value of ΔG, but they do not negate the underlying thermodynamic principles that classify a reaction as spontaneous or