I have recently come up with a discrete model in describing the adsorption of diffusive molecules to a fixed surface or interface. Briefly, the space distribution probability of each molecule is Gaussian broadened over time, thus, its pre-fractal-corrected probability of meeting another molecule or a surface is the integration of the error functions of all molecules in the solution. This operation reveals that the diffusion flux is evolving over time due to the creation of a concentration gradient near the target. Thus, the assumption of a steady-state flux in the Smoluchowski model for bimolecular reactions and the Langmuir-Schaefer model of molecular adsorption to a fixed interface are both problematic. Just like the latter model introduces several orders of magnitude variation in the adsorption rate of self-assembled monolayers, the several order of magnitude variation on the Smoluchowski rate in protein association could come from the same reason in choosing the steadystate boundary conditions during the calculation.