Carboxysome

Carboxysome is a protein-shell micro-compartment inside bacterial cell and is involved chiefly in carbon fixation. It is a cytoplasmic proteinaceous structure in the cytosol of bacteria such as Cyanobacteria and other CO₂-fixing bacteria. It is made up of polyhedral protein shells of 80-140 nm in diameter. It contains enzymes (e.g. ribulose-1,5-biphosphate carboxylase/oxygenase or RubisCO) involved in carbon fixation. Its function is to ensure that there is an adequate concentration of carbon dioxide (CO₂) for fixation. It concentrates carbon dioxide inside through co-localized carbonic anhydrase activity that produces CO₂ from bicarbonate. The protein shell of the carboxysome prevents the escape of CO₂. Having sufficient CO₂ near RuBisCO inside the carboxysome warrants carbon fixation and prevents too much photorespiration. Apart from carboxysome, other organellar-like structures in prokaryotes are chlorosome and magnetosome.

See also

• Cell
• Organelle

References

1. 4.6C: Carboxysomes. (2019, June 5). Retrieved from Biology LibreTexts website: https://bio.libretexts.org/Bookshelves/Microbiology/Book%3A_Microbiology_(Boundless)/4%3A_Cell_Structure_of_Bacteria%2C_Archaea%2C_and_Eukaryotes/4.6%3A_Specialized_Internal_Structures_of_Prokaryotes/4.6C%3A_Carboxysomes

© Biology Online. Content provided and moderated by Biology Online Editors