Give
importance
of heterocyst in BGA.
Answers
Answer:
Heterocyst
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.
Find sources: "Heterocyst" – news ·newspapers · books · scholar · JSTOR (July 2013) (Learn how and when to remove this template message)
Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale, and Anabaena sphaerica. They fix nitrogen from dinitrogen (N2) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis.[1] Nitrogenase is inactivated by oxygen, so the heterocyst must create a microanaerobic environment. The heterocysts' unique structure and physiology require a global change in gene expression. For example, heterocysts:
produce three additional cell walls, including one of glycolipid that forms a hydrophobic barrier to oxygen
produce nitrogenase and other proteins involved in nitrogen fixation
degrade photosystem II, which produces oxygen
up-regulate glycolytic enzymes
produce proteins that scavenge any remaining oxygen
contain polar plugs composed of cyanophycin which slows down cell-to-cell diffusions