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Kurs: MCAT > Rozdział 2

Lekcja 1: Biological sciences practice passage questions

The thermodynamics of ATP hydrolysis in living cells

Zadanie

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 the following equation:
ΔG=RT ln Keq
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.
ATP4+H2OADP3+Pi2+H+
ΔG=30.5kJmol
The actual change in free energy for ATP hydrolysis, symbolized by ΔG, varies according to cell type and prevailing physiological conditions. For example, table 1 reports variation in ΔG values for various rat cell types under normal physiological conditions, along with cellular ATP and ADP concentrations.
Table 1. ΔG of ATP hydrolysis, ATP concentration ([ATP]), and ADP concentration ([ADP]) for three different rat cell types under normal physiological conditions.
[ATP][ADP]ΔG of ATP hydrolysis
Hepatocyte3.38mM1.32mM34.9kJmol
Myocyte8.05mM0.93mM41.2kJmol
Neuron2.59mM0.73mM37.7kJmol
Lymphocyte2.62mM0.70mM?
Which of the following does not represent a possible explanation for the large negative ΔG for ATP hydrolysis?
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