On the relationship between membranes and ambients

We establish a relationship between two formalisms used in describing biological systems. We translate some notions from the ambient calculus into the formalism of membrane systems. Thus we consider the exhibit of an ambient, its level, the structural congruence, and the contextual bisimulation in order to define and study in membrane systems the corresponding observation barbs, the depths of a membrane system, the structural congruence and the contextual bisimulation. We describe the sodium–potassium exchange pump in both membrane systems and safe ambients. We also compare the direct description of the pump using the membrane systems with the description obtained through the translation from safe ambients.