Ultra Structure
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Transcript of Ultra Structure
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EUKARYOTE CELL ULTRASTRUCTURE
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Primary Cell Structure
That which can be seen using the light microscope
© P Billiet© 2010 Paul Billiet ODWS
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Ultrastructure
That which can be observed under the electron microscope
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EUKARYOTE CELL ULTRASTRUCTURE
20 nm diameterProtein synthesisRibosome
26 to 56 nm thickSupport, Golgi apparatus synthesis
Endoplasmic Reticulum (ER)
Cisternae: 0.5µm thick, l-3µm diameter
Secretion, reprocessing, lysosome synthesis
Golgi apparatus
0.5 to 3.0 µm diameterDigestion, recycling & isolation
Lysosome
5 to 10 µm diameterPhotosynthetic pathwaysChloroplast
1.0 to 12.5 µmRespiration pathwaysMitochondrion
10 µm diameterCell division, protein synthesis
Nucleus
DIMENSIONSMAIN FUNCTIONSORGANELLE
© 2010 Paul Billiet ODWS
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NUCLEUS (latin kernel)
TEM Nucleus of a rat hepatocyte
Image Credit: www.sinauer.com
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NUCLEUS (pl nuclei)
Usually spherical occupying up to 75% of the cell volume
10 µm
© 2010 Paul Billiet ODWS
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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
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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
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MITOCHONDRION (gk mitos = thread khondrion = granule)
Image Credit: University of Georgia
TEM of mitochondrion from mouse kidney cell
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MITOCHONDRION (pl. mitochondria)
outer membrane
inner membrane
Mitochondrial envelope
Inter membrane space
CristaeInner matrix
1.0 to 12.5 µm
© 2010 Paul Billiet ODWS
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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
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CHLOROPLAST (Gk chloros = green plast = form or shape)
Image Credit: University of Wisconsin
TEM chloroplast
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CHLOROPLAST
outer membrane
inner membrane
Chloroplast envelope
Starch grains
Grana
Frets
Thylakoid membrane
Stroma
5 to 10 µm© 2010 Paul Billiet ODWS
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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
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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
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LYSOSOME
Image Credit: http://www.biokurs.de/
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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
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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
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LYSOSOME
Function Digestion of compounds taken in by the cell by
endocytosis Recycling of material within the cell
© 2010 Paul Billiet ODWS
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GOLGI APPARATUS
Image Credit: International Journal of Morphology
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GOLGI APPARATUS
Golgi vesicles transport the materials from one cisterna to the next
Cisternae are flattened sacs
Transport vesicles bring material from the endoplasmic reticulum to the entry face
Golgi vesicles take transformed materials from the exit face to their destination
© 2010 Paul Billiet ODWS
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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
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ENDOPLASMIC RETICULUM (ER)
Image Credit: www.lifesci.sussex.ac.uk/
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ENDOPLASMIC RETICULUM (ER)
Rough ER
Smooth ER
Transport vesicles
Lumen which can occupy up to 10% of the cell volume
Membranes
© 2010 Paul Billiet ODWS
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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
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RIBOSOME
Image Credit: www.palaeos.com/
Image Credit: British Society for Cell Biology
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RIBOSOME
NOT membrane bound
Found both in pro- and eukarotes
The subunits are synthesised separately in the nucleolus of the nucleus of eukaryotes
Large ribosome subunit
Small ribosome subunit
© 2010 Paul Billiet ODWS
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RIBOSOME
Distribution in the cytoplasm• single free-floating• attached to rough ER• linked together as a POLYRIBOSOME or
POLYSOMEFunction: Protein synthesisChemical compositionProtein + RNA in other words it is a nucleoprotein
© 2010 Paul Billiet ODWS
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The relationship between organelles
Nucleus
ER
Golgi apparatus
Lysosome
Ribosomes
Endocytosis
Exocytosis
Exocytosis
© 2010 Paul Billiet ODWS