What is the primary function of lysosomes?

• A. Digest excess or worn-out organelles, food particles, and engulfed bacteria and viruses.
• B. Build new membranes.
• C. Store calcium.
• D. Produce enzymes in the cytosol.

Answer: (A)

Lysosomes function as the cell’s recycling and waste-disposal system, using acidic hydrolytic enzymes to digest macromolecules. They break down worn-out organelles, food particles, and engulfed bacteria and viruses by fusing with vesicles containing this material. The digestive enzymes work best in an acidic interior, which is maintained by proton pumps in the lysosome’s membrane. After digestion, the resulting smaller molecules can be reused by the cell. This focused role in breakdown and recycling is why digestion of waste and ingested material is the primary function.

Other descriptions don’t fit because building new membranes involves lipid synthesis and membrane assembly in the ER and Golgi, calcium storage is mainly a function of the ER and mitochondria, and lysosomal enzymes are made in the rough ER and delivered to lysosomes via the Golgi—not produced directly in the cytosol.