Emergence

The chapter opens with a review of biochemical reactions, including the concepts of free energy, enthalpy, and entropy. We recognize that reaction rates are more important in biochemical systems than is free energy alone. We relate reaction rates to the concept of activation energy and discuss how biological catalysts called enzymes reduce activation energy. We create a differential equation model of a simple biochemical reaction and explore how to simplify it by assuming that the formation of the enzyme–substrate complex is maintained in a steady state. This assumption yields a differential equation model in a single variable with two parameters. We next create a toy biochemical pathway composed of three identical such reactions and use common software to model that pathway. We find that the movement of matter through the pathway is quite insensitive to the concentration of its middle enzyme. We take a digression through the idea of genetic dominance and see that this robustness to enzyme concentration in pathways is a biochemical explanation for dominance, making dominance another example of an emergent property.