Active transport in cells is carried out by certain proteins, or molecular motors as referred in the literature, that are able to perform mechanical work within a medium where viscous forces are predominant. The underlying mechanisms that regulate the movement of molecular motors are inserted in the context of stochastic processes. The standard model introduced in the 90' by Adjari and Prost and by Magnasco to describe the directed movement in these conditions is revisited with a pedagogical character to clarify and compare the descriptions of macroscopic thermal machines with that of motors operating at nanoscale. The restrictions imposed by the second law of thermodynamics are emphasized.
molecular motors; Maxwell demon; cellular transport
