Lysosomes are electron microscopic vesicular or sac-like structure of cytoplasm that is involved in intracellular digestive activities. They are commonly called as suicidal bags. They are absent in prokaryotic cells but are present in an animal cell except R.B.C. They occur in large number in those cells which carry out a phagocytic activity like W.B.C. The plant lysosomes are called spharosomes.
Lysosomes are mostly rounded or spherical in shape and sometimes irregular. The size of the lysosome is variable and it ranges from 0.2 to 0.8µm. Lysosomes consist of a lipoproteinous membrane which encloses a fluid called a matrix. The matrix contains different types of hydrolytic or digestive enzymes. Eg; Nucleases, proteases, glycosidases.
fig:Structure of lysosomes
Lysosomes are called polymorphic cell organelles because they exist in different forms inside the same cell. On the basis of nature of matrix lysosomes are categorized into four types;
It is newly formed lysosome which contains only inactive enzymes.
It is formed by the fusion of primary lysosome with food carrying phagosome and pinosome. It contains food and active enzymes and the digestion occurs inside it.Hence, it is also called digestive vacuole.
It is also called residual bodies containing waste material and undigested food which are thrown out of the cell by exocytosis.
It is formed when there is a scarcity of foreign or outside food. In this condition, primary lysosome digests reserved food or cell organelles.