This is part of the PowerPoint that covers section 1.2 in the Cambridge Pre-U Biology course. The full PowerPoint covers the following topics: Prokaryotic cell structure, asexual reproduction, introduction to antibiotics, bacterial pathogens. It can be purchased from here: https://sellfy.com/p/5C1G/

1. MAKING SENSE OF
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• All cells can be split into two categories.
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Prokaryotic Cells Eukaryotic Cells
• The major difference is that prokaryotes don’t have a nucleus
whereas eukaryotes do.

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• Animals, plants, fungi and protoctists are all made of
eukaryotic cells, but we believe they all evolved from
simpler cells that lack a nucleus called prokaryotic
cells.
• Prokaryotic cells have some features in common with
eukaryotic cells but also many differences.
• All bacteria are examples of prokaryotic cells.
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• Although they are basic organisms they are very
important in biology.
– They can be found in a huge range of environments.
– They are responsible for the decay of organic
material.
– They are pathogens of many organisms.
– We can exploit them and use them for processes in
biotechnology.
– They contribute significantly to your health. 4

5. MAKING SENSE OFMAKING SENSE OF
Structure of prokaryotic cells
Antibiotics
Reproduction
Pathogenic bacteria
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a) Outline key structural features of prokaryotic cells including: unicellular,
1-5 m diameter, peptidoglycan cell walls, lack of membrane-bound
organelles, naked circular DNA, 70S ribosomes.
b) Outline the structure of the cell walls of Gram-positive and Gram-
negative bacteria and the significance of the structure for the use of
antibiotics.
c) Explain the mode of transmission and infection of Agrobacterium
tumefaciens as an example of a bacterial pathogen.
d) Explain the mode of action of penicillin on bacteria (as an example of an
antibiotic) and explain why penicillin does not affect viruses.
e) Outline the mechanism of asexual reproduction by binary fission in a
typical prokaryote.

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• Prokaryotes come in many
shapes and sizes but the
two main groups are the
cocci (round) and bacilli
(rod shaped).
• This often forms part of
their binomial name e.g.
Lactobacillus used to
make yogurt.

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Here is a scanning electron
micrograph of Escherichia coli
bacteria
Prokaryotes are very small (1 –
5mm diameter) compared to a
typical eukaryotic cell (can be up
to 40mm in diameter).

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You can see the size difference
nicely on this image of a
squamous epithelial cell from
a human which is covered with
many Lactobacillus bacteria.

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These bacteria are called
Staphylococcus aureus and
will be discussed later in
the course.

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• All prokaryotes possess the following structures:
• These additional structures are sometimes present:
1. Cell wall
2. Cell membrane
3. Cytoplasm
4. DNA
5. Ribosomes
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1. Capsule
2. Infolding of membrane
3. Plasmids
4. Flagella
5. Pili

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• Prevents the cell bursting and
gives bacteria it’s shape.
• Made of murein which is
peptidoglycan (a combination
of polysaccharide and
protein.)
• There are two types of cell
wall which are discussed
further in this section.
Cell wall
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• The cell membrane is
broadly the same as the
cell membrane in
eukaryotes.
• The detailed structure of
membranes is discussed
in section 1.2.
• The cytoplasm is also
similar but does not
contain a cytoskeleton.
Cell membrane
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Cytoplasm

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