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MCAT training passage: Thermodynamics of ATP hydrolysis in living cells


The free energy G of a biochemical system quantifies the capacity of the system to do mechanical work. G changes over the course of a chemical reaction. The change in G during a reaction at the biochemical standard state is written ΔG and is proportional to the standard transformed equilibrium constant Keq, according to Equation 1.
ΔG=RT ln Keq
Equation 1
ATP hydrolysis represents one of the main biochemical mechanisms through which the free energy acquired during catabolic cellular metabolism is liberated to power cellular activities.
Equation 2
The actual change in free energy for ATP hydrolysis, symbolized by ΔG, varies according to cell type and prevailing physiological conditions. Table 1 reports the variation in ΔG values for ATP hydrolysis in various rat cell types under normal physiological conditions, along with cellular ATP and ADP concentrations.
Table 1 Concentrations of ATP and ADP and ([ADP]) ΔG of ATP hydrolysis in various cell types
[ATP][ADP]ΔG of ATP hydrolysis
Which of the following does not represent a possible explanation for the large negative ΔG for ATP hydrolysis?
Choose 1 answer: