Book excerpt: Cellular Energy Metabolism and Its Regulation examines the metabolic and molecular aspects of living organisms. Beginning with a discussion of evolutionary design and its close analogy with human design, it emphasizes the notion that evolution is a process of functional design, and that the characteristics of an organism, whether morphological or molecular, were selected because of functional advantage to the organism's ancestors. Thus, the study of an enzyme, a reaction, or a sequence can be biologically relevant only if its position in the hierarchy of function is kept in mind. This book dea ...