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2.2 Prokaryotic Cells
2.2 Prokaryotic Cells
Draw and label a diagram of the
ultrastructure of Escherichia coli (E. Coli) as
an example of a prokaryote
 Use images of bacteria as seen in electron
micrographs to show the structure.
 The diagram should show the cell wall,
plasma membrane, mesosome, cytoplasm,
ribosomes, plasmid, pili, flagella and
nucleoid.
2.2 Prokaryotic Cells
Annotate your diagram with the functions
each named structure:
 cell wall – forms a protective outer layer
that prevents damage from outside and
bursting if internal pressure is too high
 plasma membrane – controls entry and
exit of substances, pumping some of them
in by active transport
 mesosome – increases the area of membrane
for ATP production. May move the DNA to the
poles during cell division
 cytoplasm – contains enzymes that catalyse
the chemical reactions of metabolism and DNA
in a region call the nucleoid. Site for metabolic
reactions
 flagella - structures protruding from the cell
wall with a corkscrew shape, using energy, they
can be rotated, to propel the cell from on area
to another unlike eukaryotic flagella, they are
solid and inflexible, working like a propeller
 ribosomes 7Os– synthesize proteins by
translating messenger RNA. (Some proteins
stay in the cell and others are secreted
 nucleoid– contains naked DNA which
stores the genetic information that controls
the cell and is passed on to daughter cells
 pili - protein filaments protruding from the
cell wall used for cell to cell adhesion when
bacteria stick together to form aggregations
of cells when two cells are exchanging DNA
during conjugation
 Plasmids -Extra-nucleoid DNA . Plasmids
can self-replicate particularly before binary
fission. They are associated with
conjunction which is horizontal gene
transfer.
 Identify structures from an electron
micrographs of E. coli shown on the next
slide.
Electron micrographs of E. coli.
Reproduction of prokaryotic cells
by binary fission
 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.
Review Questions:
Q. 1 How do prokaryotic cells divide?
A. By mitosis
B. By meiosis
C. By budding
D. By binary fission
Q.2 Which function is carried out by the flagellum of the
prokaryote?
A. Movement of food towards the cell
B. Movement of the whole cell from one place to another
C. Movement of naked nucleic acid inside the cell
D. Movement of water around the cell to speed up gas
exchange
Questions 3 and 4 refer to the following
micrograph of an E.coli bacterium undergoing
reproduction.
Q. 3 The scale bar represents 0.5 µm. How long are both
cells in total?
A. 5.0 x 10- 6 m
B. 5.0 x 10- 9 m
C. 2.5 x 10- 6 m
D. 2.5 x 10- 9 m
Q. 4 In the diagram what does label X identify?
A. Nucleoid region
B. Chromatin
C. Histones
D. Endoplasmic reticulum
Q. 5 (b) Distinguish between prokaryotic cells
and eukaryotic cells.
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(b) Draw and label a diagram of the
ultrastructure of Escherichia coli.
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(c) Annotate your diagram in (5) (b) above
with functions of each part labelled.
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