Scaling in Cells

Cells, with a few exceptions, are the fundamental biological units capable of responding to stimuli, metabolizing, growing, reproducing, and evolving. They are a pivotal example of a complex system, where their agents, proteins, form a network where each of them performs different functions aimed at transporting and transforming energy and resources. From obligate endosymbiont bacteria to neurons, cells can vary in size up to 4 orders of magnitude. This change in size is accompanied by changes in many properties, including rates and components that have the form of scaling relationships but that can be explained by different mechanisms, from simply geometric to optimization. Here we summarize some of the well-known examples of scaling laws in cells and some the their theoretical underpinnings. We conclude that a unified theory to explain the origin of many of these relationships is needed for both pure and applied purposes.