Download Prokaryotic cell structure

The Prokaryotic Cell
 Single cell organisms that lack a nuclear
membrane
 Small in size
 1-10 micrometres
The Prokaryotic Cell
 Prokaryotic cells divide by
binary fission.
 This is an asexual method of
reproduction in which a
'parental' cell divides into two
smaller but equally sized cells.
 The cells are genetically
identical and form the basis of
a reproductive clone.
Binary Fission
 (a). Reproduction signal:. E.coli replicates about
once every 40 minutes when incubated at 37o
C.
 (b). Replication of DNA: bacterial cells have a
single condensed loop of DNA. This is copied by
a process known as semi-conservative
replication to produce two copies of the DNA
molecule one for each of the daughter cells
 (c). Segregation of DNA: One DNA loop will be
provided for each of the daughter cells.
 (d). Cytokinesis: Cell separation
Prokaryotic Cell
 Population growth by binary fission will be
exponential: as time increases, the rate of
growth of population increases (until there are
not more resources for extra growth)
70s versus 80s in the Eukaryotic Cell
E. Coli EM

Note the double membrane of this E. coli .

This feature means that the cells do not
retain the dark blue stain used in
microscopy. They are therefore known as
Gram-negative this contrast with Grampositive single membrane bacteria.

2. There is some evidence in the image of pilli
which are the surrounding light grey masses.

3. In the cytoplasm of the bacterium there
are no visible organelles which is consistent
with how we expect a prokaryote cell to
appear.

4. The nucleoid region is not seen well in this
particular image but is clearer in the next
image.
The Prokaryotic Cell
 Characteristics include:
 No true distinct nucleus
 No complex, membranous organelles (Ribosomes
only)
 Most have cell walls
 Flagella (rotary type structure & not composed
w/microtubules)
 Pili used to transfer DNA from one cell to another
(sexual reproduction)
The Prokaryotic Cell
 Characteristics include:
 Nucleoid (region containing free DNA)
 Classified according to their metabolic needs
 Divide by binary fission
 No mitochondria
Exercises
 What is a disadvantage of the prokaryotic cells
having their DNA free in the cytoplasm without a
nuclear membrane
 What structures are involved in sexual
reproduction in prokaryotic cells
A bacterium walked into a restaurant.
“I’d like a pizza please” he said
“I’m sorry, we’re not doing food today,” the
waiter replied
WHY NOT??
“We don’t have the staph”
Read and outline prokaryotic
cells from your text
Stem Cells
Review Prokaryotic
Assessment Statement