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Cells
A Comparison of Eukaryotes
and Prokaryotes
What is a Prokaryote Cell?
• Most prokaryote cells are small, very
small (less than 5 micrometers), with a
simple internal stucture.
• They are surrounded by a simple
membrane to protect the bacterial cell
• This is the point of attack for antibiotics
(they affect cell wall synthesis)
A Prokaryotic Cell
• Some bacteria can
move, propelled by
flagella (different from
those in Eukaryotes)
• Surface projections
called pili (pilus sing.)
are used to attach
bacteria to surfaces or
for genetic exchange.
A Prokaryotic Cell
• Capsules or slime
layers are
polysaccharide or
protein coatings that
some diseasecausing bacteria
secrete outside their
cell wall helping
cells attach to their
host.
A Prokaryotic Cell
• Studies have been done with mutants
lacking this coating or shell and they
seem to have no harmful effects without
it.
• Unlike the elaborate cytoplasm of
Eukaryote cells Prokaryote cytoplasm is
generally very simple.
A Prokaryotic Cell
• Prokaryote cells
generally have a single
circular strand of DNA
which is coiled and
attache to the plasma
membrane and
concentrated in the
region of the cell called
the nucleoid.
A Prokaryotic Cell
• The nucleoid is not however physically separated
from the cytoplasm.
• This is a key difference, prokaryotic cells lack nulei as
well as the other membrane-enclosed organelles that
eukaryotic cells posses.
• Though this is not a strict rule, some photosynthetic
bacterial cells posses membrane bound lightcapturing proteins and enzymes.
A Prokaryotic Cell
• One of the last structure
to be mentioned about
prokaryotic cells is the
existence of ribosomes.
• These are structures
composed of proteins
and ribonucleic acid
(RNA) on which
proteins are synthesis
occurs
A Prokaryotic Cell
• Finally there may be
the existence of
food granules that
store engery-rich
materials such as
glycogen.
Comparison of Prokaryote and
Eukaryote