Thermodynamics Review

Conclusion

The first and second laws of thermodynamics are useful in helping us to understand bioenergetics, the flow of energy through living systems. They can help us determine whether a physical process, such as a biochemical reaction, is possible. Reactions that require energy input will not proceed naturally, or spontaneously. However, such energy-requiring, endergonic reactions can be coupled to spontaneous, exergonic reactions. This linking together of two chemical processes allows the energy-requiring reactions to proceed by "borrowing" energy from energy-releasing reactions. We can calculate whether a reaction is spontaneous or not with the Gibbs Free Energy, DG. The DG value and the equilibrium constant, K_eq, allow us to predict whether the products or the reactants will be more abundant at equilibrium. Understanding K_eq and Le Chatelier’s Principle also allows us to predict which way the reaction will go to reach equilibrium when extra reactants or products are present. However, Thermodynamics is not useful for determining reaction rates.