Schematic representation of the three layer MAPK cascade. The cascade is activated by incoming signal represented as “Signal”. The Signal phosphorylates M3K to M3K* where “*” represents phosphorylation. M3K* phosphorylates its downstream kinase M2K in two successive steps to M2K**. The doubly phosphorylated M2K** phosphorylates MK to MK** and MK** is the output of the MAPK cascade. The phosphatases P1, P2 and P3 dephosphorylate the kinases M3K, M2K and MK respectively. The rates v1-v10 in a sequential order represents the reaction fluxes. Here the solid lines with blunt heads correspond to dephosphorylation steps carried out by the phosphatases and dashed lines with blunt heads corresponds to phosphorylation of the cascade kinases by their respective upstream kinases.