Màster en Biofísica Part I, curs 2007-2008. Part II la trobareu a: http://hdl.handle.net/2445/6722We explore biological transport across membrane channels from a physical point of view. The main objective is to use the tools available to a physicist from non-equilibrium thermodynamics and apply them to a concrete biological problem. In this case, we focus our attention in trying to build simple physical models, yet not trivial, that match the behavior of real channels, or ones that can be synthetically accomplished. The model of a channel studied in here consists on a symmetric sawtooth potential with multiplicative noise. The introduction of multiplicative noise into the system makes it dramatically change its behavior, yet it remains analytically solvable. We also present a simulation framework applicable to more complex and realistic models for channels that can be easily mapped to real experiments and does not require cumbersome theoretical developments.