Multiple Choice
In the context of Gibbs free energy and cellular energy coupling, how many phosphate groups does ATP (adenosine triphosphate) contain?
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1. Introduction to Biochemistry
Gibbs Free Energy
Multiple Choice
In the context of Gibbs free energy and energy coupling in cells, the reaction ATP ADP ATP is best described as which of the following?
A
Substrate-level phosphorylation
B
An allosteric transition
C
A redox couple
D
A futile cycle
Verified step by step guidance1
Understand the concept of Gibbs free energy (ΔG) in biochemical reactions, which determines whether a reaction is spontaneous (ΔG < 0) or non-spontaneous (ΔG > 0).
Recognize that energy coupling in cells often involves linking an energetically unfavorable reaction to a favorable one, such as ATP hydrolysis, to drive the overall process forward.
Analyze the given reaction ATP ⇌ ADP ⇌ ATP, which implies ATP is being converted to ADP and then back to ATP without net productive work, indicating continuous cycling.
Identify that such a cycle where ATP is hydrolyzed and then resynthesized without accomplishing useful cellular work is called a futile cycle, as it wastes energy.
Compare the options: substrate-level phosphorylation involves direct synthesis of ATP, allosteric transitions involve regulation of enzyme activity, and redox couples involve electron transfer; none describe this continuous ATP-ADP cycling without net gain, confirming the answer as a futile cycle.
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