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

Why does building a protein in a cell require an input of free energy even though peptide bonds can be hydrolyzed during digestion?

A.Every covalent bond stores energy that is released as soon as the bond is broken
B.Proteases destroy chemical energy before the cell has a chance to capture it
C.Synthesis costs energy only because ribosomes move more slowly than proteases
D.Protein synthesis is driven by coupled reactions and activated intermediates, while hydrolysis follows a different reaction pathway

Explanation

Core Concept

Protein synthesis is an energy-coupled process. Amino acids are first activated on tRNAs, and translation uses additional nucleotide hydrolysis to drive accurate, directional synthesis. Protein hydrolysis follows a different chemical pathway. The contrast should not be explained by saying bond formation is inherently energy-consuming while bond breaking inherently releases energy, because breaking any chemical bond requires energy and net ΔG depends on the complete reaction.

Correct Answer

DProtein synthesis is driven by coupled reactions and activated intermediates, while hydrolysis follows a different reaction pathway

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