FUNCTIONS
(1) Intracellular digestion - Individual cells may obtain food through phagocytosis. The same is digested with the help of lysosomes. It is of two types:-
(a) Heterophagy - Digestion of foreign materials received in cell by phagocytosis and pinocytosis. Secondary lysosome performs as the intra cellular lysosomes.
(b) Autophagy - Digestion of old or worn out cell organelles. Autophagy also takes place during starvation of cell.
Ambilysosomes - Lysosomes which perform both heterophagy and autophagy.
(2) Extracellular digestion -
Lysosomes of osteoclast (bone eating cells) dissolve unwanted part of bones. Extracellular digestion by lysosomes also occur in fungi.
(3) Crinophagy -
Conversion of complex and inactive hormones into simple and active hormone through lysosome is called crinophagy. In endocrine gland the excessive secretory granules of hormones are digested by lysosomes. Release of thyroxine hormone from thyroglobulin stored in thyroid follicles is carried out by Lysosomal proteases.
Thyroglobulin → Thyroxine
(complex + inactive) Lysosomes (simple + active)
(4) Cellular digestion (Autolysis) - Digestion of whole cell through lysosomal enzymes. Sometimes all lysosomes of a cell burst to dissolve the cell completely. Old cells are removed by autolysis, unwanted organs of embryo are destroyed by autolysis, Cathepsin of lysosome digests the tail of tadpole during metamorphosis, and untimely rupture of lysosome sometimes causes mutation. (DNAase of Lysosome alter structure of DNA)