ABSTRACT
This chapter explores some of the principles that meet the qualifications of system ideas for understanding metabolism. Their adoption will help form a metabolism perspective. So too would any measurement of metabolic concentrations in cells; the idea of a compartmentation that somehow defies solution diffusion renders values of measured intermediates irrelevant. Here, the notion of collections of enzymes and new properties that emerge from different viewpoints are essential to understanding metabolic systems. The steady state is one of two great models of reaction flow, applicable to both metabolic pathways and enzymatic reactions within those pathways. Kinetics is the other pillar for analysis of metabolic regulation. However, much of the kinetic behavior of the individual reactions is different in cells from those measured in isolation: in vitro kinetic analysis requires that product formation be zero, but in a steady state it is decidedly nonzero. Thermodynamics and kinetics—two guiding principles of chemistry—are somewhat modified when applying them to biological systems.
