Explain about the Brownian ratchets and molecular motors ?

How work is carried out by molecules within biological cells is essential to understanding how cells function. A clue like how some molecular motors work was given by Listeria monocytogenes, a bacterium which causes meningitis. Bacteria penetrate host cells by taking benefit of Brownian motion, exchanging chemical for mechanical energy by utilizing the random jostling of molecules. This "Brownian ratchet" works through inserting actin monomers into gaps formed as molecules are jostled throughout polymerization, so harnessing the forces of Brownian motion in just one direction. Identifying how random Brownian motion could lead to directional movement needed complex mathematical models, and equally sophisticated models are required to understand other cell processes operating at such small scales that intuition is not extremely helpful.