Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologymediummcq1 pt

A lysosome engulfs a damaged mitochondrion and digests its proteins down to amino acids that the cell then reuses. Which description of this breakdown is correct?

A.Hydrolytic enzymes cleave peptide bonds, splitting water across each bond and releasing free amino acids
B.Dehydration synthesis adds water to the proteins and rebuilds them into new shapes
C.The amino acids are excreted unchanged because animal cells cannot recycle them
D.Oxygen gas released inside the lysosome oxidizes the peptide bonds until they snap

Explanation

Core Concept

Autophagy delivers worn organelles to lysosomes, whose acidic interior contains proteases that hydrolyze peptide bonds. Each cleavage splits a water molecule across the bond, restoring an amino group on one fragment and a carboxyl group on the other, so free amino acids return to the cytosolic pool for new protein synthesis. Building bonds would release rather than consume water, amino acid recycling is routine, and no internal oxygen gas takes part.

Correct Answer

AHydrolytic enzymes cleave peptide bonds, splitting water across each bond and releasing free amino acids

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