Question

How many types of lysosomes showing polymorphism are recognized?
A. 2
B. 3
C. 4
D. 5

Answer 1

Hint: Lysosomes are small, spherical, membrane-bound cell organelles which contain hydrolytic enzymes. They are responsible for intracellular and extracellular digestion. They are found in all animal cells and few lower plant groups.

Complete answer:
Polymorphism is a phenomenon when a structure exists in more than one form. Polymorphism is an important feature of lysosomes which is why they are called polymorphic organelles. Lysosomes exhibit four polymorphic forms. These are:

> Primary lysosomes – These are also called storage granules. They are small sac-like vesicles formed by budding off from the membrane of Golgi apparatus. They store hydrolytic enzymes secreted by ribosomes in the endoplasmic reticulum.

> Secondary lysosomes – These are also called heterophagosome. They are formed when primary lysosomes fuse with a macromolecule laden phagosome. Soon the digestion of the macromolecules takes place in presence of digestive enzymes. The digested food is passed out into the cytoplasm and undigested food remains in the lysosome.

> Residual bodies – Those lysosomes which contain only undigested food or debris are called residual bodies. Residual bodies move towards the plasma membrane and fuse with it to expel out the debris by exocytosis.

> Autophagic vacuoles – These are also called autophagosomes. They are formed when a number of primary lysosomes fuse together to digest a degenerated intracellular organelle. Digestion takes place by the process of autophagy. They provide nourishment during starvation. A liver cell during starvation may show a number of autophagosomes.

Hence, the correct answer is option (C).

Note: Lysosomes are variously named depending upon their functions. They are called disposal bags as they help in disposal of cell debris. They are also called recycling centres when digested products are made available to the cells for their functioning.