Has evolution has resulted in highly optimized cellular processes, or are the cellular networks we observe today the result of a series of accidents, highly structured but far from optimal? Put another way, do cellular pathways resemble engineered systems? Can we identify "design principles" underlying molecular interaction networks, or does contingency demand that biological systems be studied and understood on a case-by-case basis only? It is likely reality lies somewhere between these extremes.

I will argue that one of the best-studied cellular networks, the yeast galactose utilization pathway (a relatively modern evolutionary "invention"), includes several features with direct correlates to good engineering design. Specifically, we ask five questions about the detailed structure of the pathway and find that each can be explained in terms of design principles used in signal processing and control.