  We analyze both the static and dynamic fluctuation spectrum of the red-blood
cell in a unified manner, using a simple model of the composite membrane. In
this model, the two-dimensional spectrin network that forms the cytoskeleton is
treated as a rigid shell which is located at some constant average separation
from the lipid bilayer. The cytoskeleton thereby confines both the static and
dynamic fluctuations of the lipid bilayer. The predictions of the model account
for the wavevector and frequency dependence of the experimental data. The
observed amplitude of the thermal fluctuations is related to effects of
ATP-driven fluctuations.
