AS level

1. Eukaryotes and Prokaryotes

2. Prokaryotes includes
the bacteria
Karyote means nucleus
Prokaryotes do not
have a membrane
bound nucleus
The nuclear material is
free in the cytoplasm
It does not wrap around
histone proteins to form
chromosomes
DNA
Cytoplasm

3. Prokaryotes have no
membrane bound
organells
Some functions like
respiration take place
on folds of the cell
surface membrane
called mesosomes
The enzymes required
are embedded in the
membrane
Cell
membrane
mesosomes

4. Prokaryotes have 70S
ribosomes free in the
cytoplasm
70S Ribosomes

5. Prokaryotes have a cell
wall made of
peptidoglycan
This may be surrounded
by a slime capsule
Peptidoglycan cell
wall
Slime
capsule

6. Prokaryotes may have a
flagellum for movement
The structure of
proteins inside the
flagellum is different to
that in Eukaryotes
Some Prokaryotes have
many cytoplasmic
projections called Pili
Flagellum

8. Eukaryote means “true
nucleus”
Eukaryote cells have a
nucleus with a nuclear
envelope
They have membrane
bound organelles
Chloroplasts and
mitochondria have a
double membrane

9. The Endosymbiont Theory
• Chloroplasts and Mitochondria are the
same size as Prokaryotes (0.5 - 10µm)
• They contain 70S ribosomes and
circular DNA like prokaryotes
• They have a double membrane
The endosymbiont theory suggests these
organelles were once free living prokaryote
organisms that were engulfed by another
cell and enclosed in a vacuole

10. A larger prokaryotic cell engulfs a smaller
one
The smaller cell can photosynthesise because
it contains chlorophyll pigments
Note the smaller cell has its
original membrane and a
vacuolar membrane around
it
Or a double membrane

11. Instead of digesting the contents of the vacuole
a symbiotic relationship was established
Symbiotic relationships are those in which both
parties benefit from the relationship
The larger cell receives glucose
The smaller cell is sheltered and receives other
nutrients and raw materials