  Energy-based modelling brings engineering insight to the understanding of
biomolecular systems. It is shown how well-established control engineering
concepts, such as loop-gain, arise from energy feedback loops and are therefore
amenable to control engineering insight. In particular, a novel method is
introduced to allow the transfer function based approach of classical linear
control to be utilised in the analysis of feedback systems modelled by network
thermodynamics and thus amalgamate energy-based modelling with control systems
analysis. The approach is illustrated using a class of metabolic cycles with
activation and inhibition leading the concept of Cyclic Flow Modulation.
