This paper demonstrates the equivalence between simple feedback loops and the biochemcal enzyme reactions in confined media that obey Michaelis-Menten kinetics. Single and cascaded reactions are modeled, and general principles to achieve enzyme transfer functions are set out. Reaction rate and concentration difference are identified as the through and across variables of biochemical networks, and it is shown that Kirchhoff’s laws can be applied to these systems. Allosteric inhibition is examined as a way of injecting external signals into the biochemical network.