Entropic Forces in the Cell

In physics we are accustomed to four fundamental forces governing every phenomenon in the Universe. However, when dealing with heterogeneous, multiphase systems, showing aggregation and self-organisation at length scales between nanometers and micrometers, other interactions seem to appear mysteriously, inducing strange effects such as osmosis, diffusion, depletion, hydrophobicity, settling, viscous drag, and so on. Certainly, also these effects must ultimately find their origins in the four fundamental forces. But in order to master them we need to introduce statistical thermodynamics concepts, conveniently embodied in the notion of “entropic” forces. The internal dynamics of a cell, a dense fluid crowded by hundreds of different proteins, molecules, charged ions, multiple lipid membranes, appears as an ideal laboratory to study such exotic physical phenomena.