  In recent years considerable portion of the computer science community has
focused its attention on understanding living cell biochemistry and efforts to
understand such complication reaction environment have spread over wide front,
ranging from systems biology approaches, through network analysis (motif
identification) towards developing language and simulators for low level
biochemical processes. Apart from simulation work, much of the efforts are
directed to using mean field equations (equivalent to the equations of
classical chemical kinetics) to address various problems (stability,
robustness, sensitivity analysis, etc.). Rarely is the use of mean field
equations questioned. This review will provide a brief overview of the
situations when mean field equations fail and should not be used. These
equations can be derived from the theory of diffusion controlled reactions, and
emerge when assumption of perfect mixing is used.
