EN
The Feynman ratchet and pawl machine is presented to illustrate some implications of the Second Law of thermodynamics and to demonstrate how the useful work can be extracted from fluctuations. Molecular motors moving along microtubules and responsible for transporting vesicles, organelles and other substances in cells are described in terms of Brownian ratchets driven by non-equilibrium fluctuations of the ATP cycles. Models of non-thermal fluctuations are presented and used for showing the noise-induced transport phenomena in spatially periodic structures.