Mesosome is a specialised membranous structure formed by the invagination of plasma membrane in prokaryotes. These extensions are
in the form of vesicles, tubules and lamellae. 

The mesosome performs the following functions -:

1. Help in respiration, secretion processes by  increasing the surface area of the plasma membrane and enzymatic content.

2. Helps in DNA replication and distribution to daughter cells. 

4. Help in cell wall formation.