Ligand_EGF + Surface_Receptor_External -> Receptor_Ligand_Complex
Receptor_Ligand_Complex -> Surface_Receptor_External
Free_pit_proteins + Receptor_Ligand_Complex -> Receptor_Ligand_Pit_Protein_complex
Receptor_Ligand_Pit_Protein_complex -> Receptor_Ligand_Complex
Surface_Receptor_External -> Internalised_receptors
Receptor_Ligand_Complex -> Internalised_Ligand + Internalised_receptors
Receptor_Ligand_Pit_Protein_complex -> Internalised_Ligand + Internalised_receptors
Internalised_Ligand -> 0
Internalised_receptors -> Surface_Receptor_External