An acidic compartment built for demolition
The lysosome is a membrane-bound organelle whose interior is kept acidic, around pH 4.5 to 5, by a proton-pumping V-type ATPase. Its dozens of acid hydrolase enzymes, including proteases, lipases, nucleases, and glycosidases, work best at that low pH, which doubles as a safety feature: if they leak into the neutral cytosol they lose most of their activity.
These enzymes break proteins, lipids, nucleic acids, and complex carbohydrates down to their building blocks, which are then exported back to the cytosol for reuse.
What gets delivered for breakdown
Material arrives by several routes: endocytosis and phagocytosis bring in extracellular cargo and pathogens, while autophagy delivers worn-out organelles and protein aggregates. The lysosome therefore acts as both a recycling center and a quality-control hub.
Inherited defects in single lysosomal enzymes cause lysosomal storage disorders, where undegraded material accumulates. That link shows how essential continuous turnover is, and why this organelle is studied in aging and neurodegeneration research.