Which membrane-bound organelle is responsible for breaking down cellular waste?

• A. Lysosomes
• B. Ribosomes
• C. Mitochondria
• D. Lysosomes

Answer: (D)

Lysosomes are the membrane-bound organelles that break down cellular waste. They contain acid hydrolase enzymes that digest proteins, nucleic acids, carbohydrates, and lipids, and they operate best in an acidic interior. The lysosome’s membrane keeps these powerful enzymes contained, protecting the rest of the cell from their activity. They fuse with vesicles carrying material to be degraded—whether from outside the cell (phagocytosis) or from worn-out organelles inside the cell (autophagy)—and recycle the resulting molecular components for reuse. This waste-processing role is distinct from other organelles: ribosomes synthesize proteins, mitochondria generate ATP, and the lysosome specializes in breaking down and recycling macromolecules.