Ultra Structure

EUKARYOTE CELL ULTRASTRUCTURE

Primary Cell Structure

That which can be seen using the light microscope

© P Billiet© 2010 Paul Billiet ODWS

Ultrastructure

That which can be observed under the electron microscope

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

NUCLEUS (latin kernel)

TEM Nucleus of a rat hepatocyte

Image Credit: www.sinauer.com

NUCLEUS (pl nuclei)

Usually spherical occupying up to 75% of the cell volume

10 µm


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.


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


MITOCHONDRION (gk mitos = thread khondrion = granule)

Image Credit: University of Georgia

TEM of mitochondrion from mouse kidney cell

MITOCHONDRION (pl. mitochondria)

outer membrane

inner membrane

Mitochondrial envelope

Inter membrane space

CristaeInner matrix

1.0 to 12.5 µm


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


CHLOROPLAST (Gk chloros = green plast = form or shape)

Image Credit: University of Wisconsin

TEM chloroplast

CHLOROPLAST

outer membrane

inner membrane

Chloroplast envelope

Starch grains

Grana

Frets

Thylakoid membrane

Stroma

5 to 10 µm© 2010 Paul Billiet ODWS

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


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


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


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


GOLGI APPARATUS

Image Credit: International Journal of Morphology

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


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


ENDOPLASMIC RETICULUM (ER)

Image Credit: www.lifesci.sussex.ac.uk/

ENDOPLASMIC RETICULUM (ER)

Rough ER

Smooth ER

Transport vesicles

Lumen which can occupy up to 10% of the cell volume

Membranes


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


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

Large ribosome subunit

Small ribosome subunit


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


The relationship between organelles

Nucleus

ER

Golgi apparatus

Lysosome

Ribosomes

Endocytosis

Exocytosis

Exocytosis


Ultra Structure

Documents

Transcript of Ultra Structure