Page 226 - The Miracle in the Cell Membrane

The Miracle in the Cell Membrane

most delicate balance for one cell to be able to bind to
another, and it is impossible for that equilibrium to have
attained its ideal form by trial and error.

Another of the Cell's Essential Abilities:
Crawling

If cells could not move, life would be impossible.
During crawling, the cell extends fan-like protrusions
known as lamellae that permit a temporary attachment to
the adjacent surface and slide forward, dragging the cell
behind them. This process is made possible by the cell's
constantly changing shape. To do so, that the cytoplasm
inside the cell wall must have the property of a semi-
solid and be adhesive in such a way as to form protru-
sions extending to the outside. But at the same time, the
inside of the cell must also have solid structural elements
to constitute a flexible skeleton.
Evidently, the cell's crawling ability depends on the
cytoplasm being readily deformable so that the cell's inte-
rior can be drawn into an advancing protrusion. If too
viscous, the cell's contents would be immobilized. The
cell must be able to reversibly adhere to a substratum,
and, as you just saw, the property of adhesion depends
on the strength of weak chemical bonds. The cell must be
able to generate enough traction to pull its mechanically
rigid scaffold. If the viscosity of water, the energy levels
of weak chemical bonds and the power of the traction
forces were all slightly different from what they are, such

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