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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. |
