Use the following information to answer questions:

The structure of adenosine triphosphate (ATP) is shown below (Figure 1). ATP is hydrolyzed to ADP and inorganic phosphate when in equilibrium with water, and the high energy of this molecule comes from two high-energy phosphoanhydride bonds. Each bond has a ΔG of −30.5 kJ/mol. Therefore, the free energy released by hydrolysis of ATP to ADP and inorganic phosphate under standard conditions, ∆G°´, is equal to −30.5 kJ/mol at pH 7.0.

 

MCAT Chemical and Physical Foundations of Biological Systems 10

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4 Questions

1. The value for ∆G°´ indicates that ATP hydrolysis is

endothermic.exergonic.endergonic.exothermic.

2. The nucleoside component of ATP is a

porphyrin.flavin.purine.pyrimidine.

3. The observed ∆G°´ for ATP hydrolysis to ADP and inorganic phosphate CANNOT be attributed to

lower solvation of inorganic phosphate, H+, and ADP relative to ATP.greater resonance stabilization of ADP relative to ATP.electrostatic repulsions among the negative oxygen atoms in ATP.higher disorder and lower free energy in ADP relative to ATP.

4. The following table provides the concentrations of ATP, ADP, and Pi in human erythrocytes:

Given that the constant R is equal to , and assuming equilibrium at pH 7.0 and body temperature of 37°C, what is the free energy of hydrolysis of ATP under these conditions?

–8.5 kJ/mol–52 kJ/mol–41 kJ/mol–33 kJ/mol