Final answer:
The extent to which reactants spontaneously convert to products in a biochemical reaction is expressed by the equilibrium constant (Keq). A negative ΔG indicates spontaneity, but temperature changes can affect this, highlighting thermodynamics and kinetics' influence.
Step-by-step explanation:
In the context of a biochemical reaction, the extent to which reactants are converted to products spontaneously is expressed by the equilibrium constant (Keq). The Keq is a value that indicates the ratio of the concentrations of the products to reactants at equilibrium at a given temperature. As such, if ΔG, the change in free energy, is negative, the reaction is considered spontaneous, meaning it can occur without additional energy input. Conversely, a positive ΔG suggests that the reaction is nonspontaneous and will require energy to proceed.
It's also important to note that changing the temperature can significantly affect the spontaneity of the reaction. For example, the synthesis of ammonia from nitrogen and hydrogen is thermodynamically spontaneous under standard conditions. However, increasing the temperature can lead to the -TΔS term becoming dominant, leading to a situation where the reaction is no longer spontaneous at high temperatures, reflected by a Keq that is less than one.
Lastly, it is crucial to distinguish between spontaneous reactions and reaction kinetics. While a reaction may be spontaneous, it may still occur too slowly to be practical without a catalyst or other methods to increase the reaction rate. This highlights the difference between thermodynamics (spontaneity) and kinetics (rate of reaction).