The cell walls of prokaryotes differ in molecular composition
and construction from those of eukaryotes. As you read
in Chapter 5, eukaryotic cell walls are usually made of cellulose
or chitin. In contrast, most bacterial cell walls contain
peptidoglycan, a network of modified-sugar polymers cross·
linked by short polypeptides. This molecular fabric encloses
the entire bacterium and anchors other molecules that extend
from its surface. Archaeal cell walls contain a variety of polysaccharides
and proteins but lack peptidoglycan.
Now let's look more closely at the three main types of fibers
that make up the cytoskeleton (Table 6.1). Microtubules are
the thickest of the three typesj microfilaments (also called
actin filaments) are the thinnest; and intermediate filaments
are fibers with diameters in a middle range.