What are types of lysosomes and their functions?
Posted October 2, 2023
There are four types of lysosomes based on their morphology and function.
- Primary Lysosomes are newly pinched-off vesicles from the Golgi apparatus. They are membrane-bound, small in size, and contain inactive hydrolytic enzymes in the form of granules. Primary lysosomes fuse with endosomes to become fully functional.
- Secondary Lysosomes are vesicles that are formed by the fusion of primary lysosomes that contain hydrolytic or digestive enzymes with food containing phagosomes. On fusing, the digestive enzymes get activated and work on breaking down the enclosed materials. The digested food passes out into the cytoplasm, leaving the secondary lysosome with undigested food. Secondary lysosomes are also known as digestive vacuoles or hetero-phagosomes.
- Residual Bodies are also called residual lysosomes or tertiary lysosomes. These are lysosomes that contain only indigestible food materials. The residual bodies move outward and fuse with the plasma membrane, from where they are able to expel the debris into the external environment by the process of exocytosis. Sometimes exocytosis fails, trapping the residual bodies inside the cell, which can lead to various pathological diseases such as hepatitis, Tay-Sachs disease, polynephritis, and Pompe’s disease.
- Autophagic Vacuoles are formed by the fusion of multiple primary lysosomes to eliminate damaged, worn out or aged cellular components as well as extracellular substances. The cell debris is digested through autophagy and the newly digested substances are made available to the cell for re-use or to nourish the cell during starvation. Autophagic vacuoles are also known as Auto-phagosomes, Auto-lysosomes.