Preface

The cells of our bodies represent a very large class of systems whose structural components often are both complex and soft. A system may be complex in the sense that it may comprise several components having quite different mechanical characteristics, with the result that the behavior of the system as a whole reflects an interplay between the characteristics of the components in isolation. The mechanical components themselves tend to be soft: for example, the compression resistance of a protein network may be more than an order of magnitude lower than that of the air we breathe. Cells have fluid interiors and often exist in a fluid environment, with the result that the motion of the cell and its components is strongly damped and very unlike ideal projectile motion as described in introductory physics courses. While some of the physics relevant to such soft biomaterials has been established for more than a century, there are other aspects, for example the thermal undulations of fluid and polymerized sheets, that have been investigated only in the past few decades.

The general strategy of this text is first to identify common structural features of the cell, then to investigate these mechanical components in isolation, and lastly to assemble the components into simple cells. The initial two chapters introduce metaphors for the cell, describe its architecture and develop some concepts needed for describing the properties of soft materials. The remaining chapters are grouped into three sections. Parts I and II are devoted to biopolymers and membranes, respectively, treating each system in isolation. Part III combines these soft systems into complete, albeit mechanically simple, cells; this section of the text covers the cell cycle, various aspects of cell dynamics, and some molecular-level biophysics important for understanding cell function.