AUTOPOIESIS AND (M,R) SYSTEMS IN METABOLIC NETWORKS J. C. Letelier (1) and A. N. Zaretzky (2) (1) Laboratorio de Neurobiología y Biología del Conocer. Departamento de Biología - Universidad de Chile. Casilla 653 Santiago - Chile. E-mail: letelier@uchile.cl (2) Grupo de Dosimetría de Radiaciones Ionizantes. Centro Atómico Ezeiza. Comisión Nacional de Energía Atómica. Av. Del Libertador 8250 - (1429) Buenos Aires - Argentina. E-mail: zaretzky@cae.cnea.gov.ar Abstract: Metabolism-repair systems ((M,R)) were introduced by Robert Rosen as an abstract representation of cell metabolic activity. The representation was obtained in the context of Relational Biology, which means that organization prevails over the physico- chemical structure of the components involved. This fact was determinant for algebraically formalizing (M,R) systems using the theory of categories. Two elements are considered in the construction of (M,R) systems: the metabolic activity (M) and the repair functions (R) acting on the unities of the metabolic process. The metabolic system M is considered as an input-output system. In the categorical representation, inputs and outputs are the objects of the category and the processes connecting these elements are represented by the arrows of the category. Autopoiesis is a concept developed by Humberto Maturana and Francisco Varela in order to analyze the nature of living systems. It takes into account the circular organization of metabolism and it redefines the concepts of structure and organization. Any system can be decomposed into processes and components, which interact through processes to generate other components. The definition of an Autopoietic system considers that “it is organized as a bounded network of processes of production, transformation and destruction of components that produces the components which: a)through their interactions and transformations continuously regenerate and realize the network of processes (relations) that produced them and b)constitute it (the machine) as a concrete entity in the space in which they (the components) exist by specifying the topological domain of its realization as such a network”. Both concepts were recently connected in a paper of J.C. Letelier et.al., determining that the set of autopoietic systems is a subset of the set of general abstract (M,R) systems. In fact, every specific (M,R) system is an autopoietic one, being the boundary the main element of autopoietic systems which was not formalized in Rosen's representation of (M,R) systems. This paper introduces the definition of the boundary - the physical boundary and the functional one - for (M,R) systems in the context of the categorical representation, inducing then the same kind of formalization for autopoietic systems. The concept of complete (M,R) system is also introduced as well as evidences for the functoriality and universality of the completion process. Key-words: Autopoiesis - (M,R) Systems- Relational Biology- Metabolic Networks- Theory of Categories.