How do lysosomes digest unwanted materials inside cells?

Lysosomes digest unwanted materials by utilizing an acidic interior maintained by a proton pump, which activates a variety of hydrolytic enzymes known as acid hydrolases. These enzymes break down complex macromolecules, such as proteins, nucleic acids, and polysaccharides, into simpler components like amino acids and nucleotides that the cell can recycle.1

Lysosomes receive materials for degradation through three primary pathways:

• Endocytosis: Extracellular materials are taken up into the cell within vesicles called endosomes, which then fuse with lysosomes.1
• Autophagocytosis: Old or malfunctioning organelles are enveloped by internal membranes to form autophagosomes, which deliver their contents to lysosomes for degradation.12
• Phagocytosis: Specialized cells engulf large particles, such as dead cells or bacteria, and target them for lysosomal digestion.1

The acidic environment is critical because these enzymes are only active at a low pH, which protects the rest of the cell from accidental self-degradation should a lysosome leak or rupture.1