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Skip navigation Cytoplasm-Ribosomes-Inclusions

Prokaryotic cell ribosomes

The prokaryotic ribosomes (70 S), like those of eukaryotes, are comprised of two subunits that are not always connected. The smallest subunit is 30 S, and the largest is 50 S.

They are made up of rRNA and proteins. They have a somewhat different composition from those of eukaryotes, which makes it possible to use some antibiotics against pathogenic bacteria that destroy them. Its function is to synthesize proteins.


The inclusions are scattered throughout the cytoplasm, without being surrounded by any membrane or protein envelope. They correspond to reserve granules that the bacterium has synthesized in moments of abundance of food, and to residues of its metabolism.

Gaseous vesicles

They are hollow formations of more or less spherical shape, which contain gas.

Vesicles are made up of a protein membrane that is impervious to water and solutes, but allows gases to pass through.

They regulate the buoyancy of the bacteria that possess them, such as purple and green photosynthetic bacteria, allowing them to reach depth with the optimal light intensity for their development.


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