The following reactions occur during the catabolism of glucose. Which are exergonic? Which is endergonic? Which proceeds farthest toward products at equilibrium?


b. Phosphoenol pyruvate + H₂O → Pyruvate + Phosphate(P_i)
∆G = ―14.8 kcal/mol (―61.9 kJ/mol)

Verified step by step guidance

1. Identify the type of reaction based on $\mathrm{\Delta }G$: A negative $\mathrm{\Delta }G$ indicates an exergonic reaction, meaning it releases energy.
2. Determine if the reaction is endergonic or exergonic: Since $\mathrm{\Delta }G=-14.8\text{ kcal/mol}$, the reaction is exergonic.
3. Assess the extent of reaction towards products: An exergonic reaction with a large negative $\mathrm{\Delta }G$ typically proceeds far towards products at equilibrium.
4. Understand the concept of equilibrium: At equilibrium, the reaction has reached a state where the rate of the forward reaction equals the rate of the reverse reaction.
5. Conclude the analysis: The given reaction is exergonic and proceeds far towards products at equilibrium due to its large negative $\mathrm{\Delta }G$.

Key Concepts

Exergonic Reactions

Exergonic reactions are chemical processes that release energy, typically characterized by a negative change in Gibbs free energy (∆G). In the context of glucose catabolism, these reactions are spontaneous and proceed in the direction of product formation, contributing to the overall energy yield of cellular respiration.

Endergonic Reactions

Endergonic reactions require an input of energy to proceed, resulting in a positive change in Gibbs free energy (∆G). These reactions are non-spontaneous and often involve the synthesis of complex molecules from simpler ones, which is essential for cellular functions but must be coupled with exergonic processes to drive them forward.

Equilibrium in Chemical Reactions

Equilibrium in chemical reactions refers to the state where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. The position of equilibrium can be influenced by factors such as temperature and concentration, and reactions that proceed farthest toward products at equilibrium typically have a large negative ∆G, indicating a strong tendency to form products.