What are mesosomes and what are their functions?
Mesosomes, as located via the electron micrographs, are additional, folded protuberances or membranous elaborations (could be in the form of vesicles, tubules, lamellae) that occur irregularly at the inward side of the cell membrane of the prokaryotic organisms like certain cyanobacteria, nitrogen-fixing bacteria (e.g Azotobacter), sporulating bacteria, etc. It is to be noted here that not all the Prokaryotic cells have mesosomes.
The major function of mesosomes is to increase the surface area of the plasma membrane. This drastic increase in the surface area of the membrane mainly helps the cell to carry out cellular respiration more efficiently.
This is requisite because, unlike the Eukaryotic cells, the Prokaryotic cells lack membrane-bound cell organelles. In case of of Eukaryotic cells, numerous finger-like projections or cristae in the Mitochondrion wall carry out cellular respiration. An analogy can be created, in this way, between these and the mesosomes in the Prokaryotic cells.
Mesosomes are also thought to aid in photosynthesis, cell secretions/enzymes, electron transport, cell division, cell wall formation, DNA replication and even cell compartmentalisation. Though not separate or independent cell structures, Mesosomes can be chemically induced in bacteria.
Mesosome are of two types:
- Septal mesosomes that extend from the plasma membrane towards the centre in the cell cytoplasm and are associated with nuclear material)
- Lateral mesosomes that are located at the periphery and need not be associated with nucleus.