Question

What are the cell inclusions in a prokaryotic cell?

Answer 1

Cell inclusions are non-living structures present in the cytoplasm of a prokaryotic cell. The cell inclusions may occur freely inside the cytoplasm (e.g., cyanophycean granules, volutin or phosphate granules, glycogen granules) or covered by 2-4 nm thick non-lipids, non-unit protein membrane (e.g., gas vacuoles, carboxysomes, sulphur granules, PHB granules). On the basis of their nature, the cell inclusions are of 3 types - gas vacuoles, inorganic inclusions, and food reserve.

1. Gas vacuoles - They are gas storing vacuoles found in cyanobacteria, purple and green bacteria and a few other planktonic forms. They protect the bacteria from harmful radiations.
   
2. Inorganic inclusions - They include volutin granules, sulphur granules, iron granules, magnetic granules, etc. They help the bacteria to orientate themselves along geomagnetic lines
   
3. Food reserve - Blue-green algae have cyanophycean starch, lipid globules, and cyanophycin or protein granules. In bacteria, starch is replaced by glycogen.