Thesis-PDF - IAP/TU Wien

Figure 4.13: On top a swimming Euglena. The schematic drawing depicts
a transverse section of its cell surface. Details of the articulating S-shaped
strips of the membrane skeleton and the infrastructure associated with strip
overlap. The position of the skeleton and the bridges are well suited to
mediate the sliding of adjacent strips occurring during shape changes. The
portion of the plasma membrane not subtended by the cytoskeleton may
provide the fluid region, which accommodates sliding as well as a region for
the insertion of new strips during surface replication. The traversing fiber is
positioned to maintain the S-shaped configuration and it may contribute an
elastic component to the sliding skeleton. MAB1 and MAB2, microtubule
associated bridges; MIB-A and MIB-B, microtubule independent bridges;
PM, plasma membrane; T, traversing fiber. ([91])
Microtubuli
In cell biology microtubuli (MT) are almost omnipresent, e.g. playing a major role
during cell division, are part of most cell architecture and can be found in cilia
and flagella. Microtubuli are hollow tubes with an outer diameter of 24 nm and
within their structure the position of every atom is precisely defined. A joy for
every nanotechnologist! They are also an important ingredient to the structure
and function of the pellicular strips. The tubes are built from smaller subunits,
heterodimers, each of which are composed by two proteins, the so-called α− and
β-tubulin. A schematic drawing how a flagellum is constructed from microtubuli
is given in Fig. 4.14.
What makes microtubuli so special apart from having favorable mechanical
properties is the following: The tubes have an associated direction (see Figs. 4.14,
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