Using what you have learned about changes in Gibbs free energy, would you predict the ∆G value of catabolic reactions to be positive or negative? What about anabolic reactions? Justify your answers using the terms 'enthalpy' and 'entropy.'

Verified step by step guidance

1. Begin by understanding Gibbs free energy (∆G), which is a measure of the spontaneity of a reaction. A negative ∆G indicates a spontaneous reaction, while a positive ∆G indicates a non-spontaneous reaction.
2. Recall that catabolic reactions involve the breakdown of complex molecules into simpler ones, releasing energy in the process. This release of energy typically results in a negative ∆G value, indicating that these reactions are spontaneous.
3. Consider the role of enthalpy (∆H) in catabolic reactions. These reactions often release heat, leading to a decrease in enthalpy. A decrease in enthalpy contributes to a negative ∆G value.
4. Examine the concept of entropy (∆S), which is a measure of disorder. Catabolic reactions increase entropy as they break down complex molecules into simpler ones, contributing to a negative ∆G value.
5. Analyze anabolic reactions, which involve the synthesis of complex molecules from simpler ones, requiring an input of energy. This energy input typically results in a positive ∆G value, indicating that these reactions are non-spontaneous. Anabolic reactions often involve an increase in enthalpy and a decrease in entropy, both contributing to a positive ∆G value.

Key Concepts

Gibbs Free Energy (∆G)

Gibbs Free Energy (∆G) is a thermodynamic quantity that indicates the amount of energy available to do work in a system at constant temperature and pressure. A negative ∆G indicates a spontaneous process, while a positive ∆G suggests a non-spontaneous process. It is calculated using the equation ∆G = ∆H - T∆S, where ∆H is the change in enthalpy, T is the temperature, and ∆S is the change in entropy.

Catabolic Reactions

Catabolic reactions involve the breakdown of complex molecules into simpler ones, releasing energy in the process. These reactions typically have a negative ∆G, indicating they are spontaneous. The breakdown of molecules increases entropy (∆S) and often releases heat, resulting in a decrease in enthalpy (∆H), both contributing to a negative ∆G.

Anabolic Reactions

Anabolic reactions are processes that build complex molecules from simpler ones, requiring an input of energy. These reactions usually have a positive ∆G, meaning they are non-spontaneous and require energy input. Anabolic processes decrease entropy (∆S) as they create order, and they often involve an increase in enthalpy (∆H) due to the energy required to form new bonds.