Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologyhardmcq1 pt

Cells power unfavorable processes by coupling them to ATP hydrolysis. Which description of that hydrolysis step is correct?

A.Water attacks the terminal phosphate, splitting ATP into ADP and inorganic phosphate while releasing free energy for coupled work
B.A phosphate is added to ATP, converting it into a higher-energy store
C.Water serves only as passive solvent while ATP breaks apart unaided
D.Hydrolysis absorbs energy, which is later repaid when ATP resynthesizes

Explanation

Core Concept

Hydrolysis inserts water across the phosphoanhydride bond furthest from the adenosine. The products, ADP and inorganic phosphate, sit at lower free energy than ATP, so the reaction releases energy that enzymes couple to muscle contraction, membrane transport, or biosynthesis. The phosphate leaves ATP rather than joining it, and water acts as a genuine reactant whose H and OH join the two fragments instead of serving merely as background solvent.

Correct Answer

AWater attacks the terminal phosphate, splitting ATP into ADP and inorganic phosphate while releasing free energy for coupled work

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