Crowding, diffusion, and biochemical reactions.

Diffusion is the basic mode of transport for molecules in living cells. Diffusion leads to dispersion of individual molecules, but it is also the driving force behind biochemical reactions and pattern formation as diffusional motion mediates reactant encounters. Owing to macromolecular crowding in all cellular fluids and biomembranes, diffusion of molecules in cells is quite different from the motion observed in dilute solutions in a test tube. Hindered and anomalous diffusion are seen in cells, and biochemical reactions are affected by these. This review is intended to give an introduction and a brief overview about causes and consequences of crowding-induced diffusion anomalies and their impact on biochemical reactions.