Why do lysosomes eat the cell?

Lysosomes ‘eat’ the cell as part of their cleanup process, which plays a critical role in cellular homoeostasis and waste management. Lysosomes are membrane-bound cellular organelles that contain various hydrolytic enzymes that break down and digest cellular waste materials, damaged organelles, and foreign substances or pathogens. 

When a cell is in a metabolic crisis, such as when a pathogen enters the cell, the hydrolytic enzymes in lysosomes trigger a process known as phagocytosis. Phagocytosis is a series of actions aimed at destroying the pathogen. During phagocytosis, a section of the immune cell’s plasma membrane folds in or invaginates and surrounds the extracellular material. The invaginated section pinches itself off from the immune cell’s membrane with the pathogen inside it. This newly formed structure, known as a vesicle, fuses with a lysosome present inside the immune cell. This fusion brings the pathogen in contact with the lysosome’s hydrolytic enzymes, which enzymatically degrades the pathogen. 

This invagination of the cellular membrane and its enzymatic degradation by lysosomal enzymes is often referred to as eating the cell.