There are significant differences between the conditions for chemical and biochemical reactivity. Therefore, models for treating chemical reactions are mostly not suitable for investigating interactions and transformations of bio(macro)molecules. Common features of numerous processes occurring in vivo and in vitro (such as the role of water, ions, and colloids and the significance of Helmholtz energy surfaces) are outlined. Some characteristics of a model suitable for studying van der Waals interactions between biomacromolecules, based on Brownian dynamics and the Lifshitz theory, are described.