Microbiology Demystified

surface and also aid in movement of the cell. Flagella and cilia are comprised of
axoneme microtubules. An axoneme microtubuleis a long, hollow tube made
of protein called a tubulin.

CELL WALL

Many eukaryotic cells have a cell wall. The composition of the cell wall differs
with each organism. For example, the cell walls of many fungi are composed of
chitin cellulose. Chitinis a polysaccharide, which is a polymer of N-acetylglu-
cosamine (NAG) units. The cell wall of other fungi is made of cellulose, which
is also a polysaccharide. Cellulose is also found in the cell wall of plants and
many algae. Yeast has a cell wall composed of glucanand mannan, which are
two polysaccharides.
In contrast, protozoa have no cell wall and instead have a pellicle. Apellicle
is a flexible, proteinaceous covering. Eukaryotic cells of other organisms (such
as animals) that lack a cell wall have an outer plasma membrane that serves as
an outside cover for the cell. The outer plasma membrane has a sticky carbo-

CHAPTER 4 Prokaryotic and Eukaryotic Cells^79

CI

PV F

DV

SV GA

PL

AV

RB

CGE

CHMT

N

P M

CRNU

P

RER

R

M

G

PM SER

LD

Fig. 4-6. A eukaryotic cell.