Beginning with a model of a system of enzyme reactions used by Ruth and her collaborators, connections between results on queueing network models and chemical reaction network models used in systems biology will be explored, including product form stationary distributions, Burke's theorem, fluid limit approximations, heavy traffic limits, and, perhaps, large deviations. Much of the work I will discuss grew out of a group effort catalyzed by the 2003-2004 IMA program Probability and Statistics in Complex Systems: Genomics, Networks, and Financial Engineering