Multiple Choice
In the context of Gibbs free energy and ATP hydrolysis, how many phosphate groups does adenosine triphosphate (ATP) contain?
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1. Introduction to Biochemistry
Gibbs Free Energy
Multiple Choice
In the context of Gibbs free energy, energy is released from ATP when which process occurs?
A
ATP binds to an enzyme active site without bond cleavage, and the binding alone releases usable cellular energy as a strongly exergonic step.
B
ADP is phosphorylated to ATP, which has a negative Gibbs free energy change ().
C
ATP is hydrolyzed to ADP and inorganic phosphate (Pi), resulting in a net decrease in Gibbs free energy ().
D
ATP is synthesized from AMP and pyrophosphate (PPi), releasing energy because entropy decreases.
Verified step by step guidance1
Understand that Gibbs free energy change (\$\(\Delta\) G\$) indicates whether a process releases or requires energy; a negative \$\(\Delta\) G\$ means the process is exergonic and releases energy.
Recognize that ATP hydrolysis involves breaking the terminal phosphate bond of ATP, converting it into ADP and inorganic phosphate (Pi).
Recall that this hydrolysis reaction has a negative \$\(\Delta\) G\$, meaning it releases usable energy that cells can harness for various biochemical processes.
Note that simply binding ATP to an enzyme without bond cleavage does not release significant energy, and phosphorylation of ADP to ATP actually requires energy input (positive \$\(\Delta\) G\$).
Conclude that the key energy-releasing step is the hydrolysis of ATP to ADP and Pi, which results in a net decrease in Gibbs free energy (\$\(\Delta\) G < 0\$).
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