EUKARYOTE CELL
ULTRASTRUCTURE
Primary Cell Structure
That which can be seen using the light microscope
© 2010 Paul Billiet ODWS
© P Billiet
Ultrastructure
That which can be
observed under the
electron microscope
EUKARYOTE CELL
ULTRASTRUCTURE
ORGANELLE
MAIN FUNCTIONS
DIMENSIONS
Nucleus
Cell division, protein
synthesis
10 µm diameter
Mitochondrion
Respiration pathways
1.0 to 12.5 µm
Chloroplast
Photosynthetic pathways
Lysosome
Digestion, recycling &
isolation
0.5 to 3.0 µm diameter
Golgi apparatus
Secretion, reprocessing,
lysosome synthesis
Cisternae: 0.5µm thick,
l-3µm diameter
Endoplasmic
Reticulum (ER)
Support, Golgi apparatus
synthesis
26 to 56 nm thick
Ribosome
Protein synthesis
© 2010 Paul Billiet ODWS
5 to 10 µm diameter
20 nm diameter
NUCLEUS (latin kernel)
TEM Nucleus of a
rat hepatocyte
Image Credit: www.sinauer.com
NUCLEUS (pl nuclei)
10 µm
Usually spherical occupying up to 75% of the cell volume
© 2010 Paul Billiet ODWS
NUCLEUS
Chemical composition
 Protein: Up to 90%,
HISTONES rich in basic amino acids.
 Deoxyribonucleic Acid (DNA)
about 20% (acidic)
 Ribonucleic Acid (RNA) 5 to 20%
 Nuclei usually contain about 10% CHROMATIN
= Histone + DNA = NUCLEOPROTEIN.
© 2010 Paul Billiet ODWS
NUCLEUS
Functions




Main site of DNA in eukaryotic cells
Preservation, replication and expression of
genetic information
It makes RNA for protein synthesis
It copies DNA for cell division
© 2010 Paul Billiet ODWS
MITOCHONDRION (gk mitos =
thread khondrion = granule)
TEM of
mitochondrion from
mouse kidney cell
Image Credit: University of Georgia
MITOCHONDRION (pl. mitochondria)
Inner matrix
Cristae
Inter membrane space
outer
membrane
Mitochondrial
envelope
inner
membrane
1.0 to 12.5 µm
© 2010 Paul Billiet ODWS
MITOCHONDRION
Pigments Cytochromes
Functions
 The inner membrane contains the enzyme necessary for
the synthesis of Adenosine Triphosphate (ATP)
 The mitochondria are closely associated with the
pathways of respiration
 These metabolic pathways are divided up and supported
by the membranes
© 2010 Paul Billiet ODWS
CHLOROPLAST (Gk chloros = green
plast = form or shape)
TEM chloroplast
Image Credit: University of Wisconsin
CHLOROPLAST
Grana
Thylakoid
membrane
Frets
Chloroplast
envelope
outer
membrane
inner
membrane
Stroma
© 2010 Paul Billiet ODWS
Starch grains
5 to 10 µm
CHLOROPLAST
Pigments Mainly chlorophylls with carotenoids
and others
Function: Photosynthesis
 The metabolic pathways are closely associated
with the membranes as in the case of the
mitochondrion
© 2010 Paul Billiet ODWS
Organelles and evolution





Both chloroplasts and mitochondria are double membrane
bound
They involved in energy reactions
They contain extranuclear DNA and characteristic small
ribosomes of their own
This has led biologists to believe that there may be some
similarity in their origins in the cells of eukaryotes.
The endosymbiotic theory
© 2010 Paul Billiet ODWS
LYSOSOME
Image Credit: http://www.biokurs.de/
LYSOSOME


Not discovered by electron microscopy but by
centrifugation and enzyme analysis
Some scientists suggest that they are not present in plant
cells
Structure: Simple, spherical, single membrane bound

Lysosomes contain a large number of CATABOLIC
enzymes. Catabolic enzymes digest materials by
hydrolysis
© 2010 Paul Billiet ODWS
Enzymes found in lysosomes
ENZYME
SUBSTRATE
Acid phosphatase
Phosphate esters
Acid ribonuclease
RNA
Acid deoxyribonuclease
DNA
Glycosidases
Polysaccharides
Protease
Proteins and peptides
Lipase
Lipids
Phospholipase
Phospholipids
More than 40 types of enzymes are known to occur in lysosomes.
© 2010 Paul Billiet ODWS
LYSOSOME
Function
 Digestion of compounds taken in by the cell by
endocytosis
 Recycling of material within the cell
© 2010 Paul Billiet ODWS
GOLGI APPARATUS
Image Credit: International Journal of Morphology
GOLGI APPARATUS
Golgi vesicles take transformed
materials from the exit face to
their destination
Golgi vesicles
transport the
materials from one
cisterna to the next
Cisternae
are flattened
sacs
© 2010 Paul Billiet ODWS
Transport vesicles bring
material from the
endoplasmic reticulum to
the entry face
GOLGI APPARATUS
Functions
 Processing and packaging
 Synthesising lysosomes to contain the
potentially dangerous catabolic enzymes
 Producing secretory vesicles e.g. mucus
 Making more plasma membrane
© 2010 Paul Billiet ODWS
ENDOPLASMIC RETICULUM
(ER)
Image Credit: www.lifesci.sussex.ac.uk/
ENDOPLASMIC RETICULUM
(ER)
Rough ER
Smooth ER
Transport
vesicles
Membranes
© 2010 Paul Billiet ODWS
Lumen which
can occupy up to
10% of the cell
volume
ER Functions





Not easy to study the ER is that it is difficult to extract
intact
ER starts the biosynthetic pathways form many protein
and lipid molecules in the cell
These continue in the Golgi apparatus
Rough ER has ribosomes attached to it as opposed to
Smooth ER
The proteins are made on rough ER will eventually be
secreted outside the cell
© 2010 Paul Billiet ODWS
RIBOSOME
Image Credit: www.palaeos.com/
Image Credit: British Society for Cell Biology
RIBOSOME



NOT membrane
bound
Found both in pro- and
eukarotes
The subunits are
synthesised separately
in the nucleolus of the
nucleus of eukaryotes
© 2010 Paul Billiet ODWS
Large ribosome
subunit
Small ribosome
subunit
RIBOSOME
Distribution in the cytoplasm
•
•
•
single free-floating
attached to rough ER
linked together as a POLYRIBOSOME or
POLYSOME
Function: Protein synthesis
Chemical composition
Protein + RNA in other words it is a nucleoprotein
© 2010 Paul Billiet ODWS
The relationship between
organelles
Exocytosis
Endocytosis
ER
Exocytosis
Nucleus
Ribosomes
Golgi
apparatus
Lysosome
© 2010 Paul Billiet ODWS