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Q.
In many bacteria, the cell membrane becomes invaginated and folded to form
AMUAMU 2005
Solution:
Mesosomoes are mainly found in Gram positive bacteria. They are infolding of plasma membrane in the form of vesicles/ tubules/lamellae. The term was given by Fitzjames and it is of two types
(i) Central mesosome helps in separation of nucleoid and septa formation.
(ii) Peripheral mesosome helps in strong respiratory enzymes.
Pili are of size $1 \,\mu m$ and are made up of protein pilin. They are hollow from inside and does not help in motility. The most common type of pili found are sex pilus which serve as a part of entry of genetic material during conjugation.
Inner membrane of mitochondria is folded to form cristae (Palade) to increase surface area and shape of cristae is plate like (fungi), vesicled (Euglena), knob like, finger like, etc. It bears electron transport chain and oxysomes.
Fimbriae are straight bristle like appendages and function as organ of adhesion.