Download Eukaryotic cells

Eukaryotic microorganisms and viruses
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Heribert Cypionka
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What is the main difference between the prokaryotic
and the eukaryotic cell?
● Compartimentation
>> Separation of reaction rooms
>> More complex regulation
>> Transport including fusion and
separation of membrane vesicles
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The eukaryotic cell and its structure
Size + microscopy techniques
Nucleus
Mitochondria, hydrogenosomes
Chloroplasts
Endoplasmic reticulum and Golgi complex
Lysosomes and peroxisomes
Microfilaments and microtubules
Flagella and cilia
Life cycle
Differences between prokaryotes and eukaryotes
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Size
Surface of a mouth mucosa cell of a healthy
female student from the University of Oldenburg
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Size
"Microsomes" - many
organells are
bacterium-sized
Structures smaller
than bacteria are
hardly resolved by
light microscopy
Cytoplasm of the same mouth mucosa cell
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Principles of microscopy
● Bright field
● Staining
● TEM: Contrasting + short wavelength
● Phase contrast
(differential interference
contrast, DIC, needs polarisation and beam-splitting prismas)
● Dark field
● Epifluorescence
● Confocal laser scanning microscopy
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bright field
phase contrast
dark field
DIC
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● Come-back of light microscopy...
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Pictures: Erhard Rhiel
Electron microscopy
● Negative staining
● Contrasted Section
TEM = Transmission
electron microscopy
● Freeze etching +
oblique sputtering
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Scanning electron microscopy (SEM )
Object
Detector screen
Scanning beam
Picture: Henrik Sass
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● The image is not projected to the
detector screen, but calculated from
dark and bright pixels obtained from
scanning!
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Prokaryotes: Nucleoid
Eukaryotes: Nucleus
Nucleus
● The nucleus normally
contains several linear
chromosoms with telomers
● DNA is embedded in
histons
● Large part of the DNA
is non-coding introns,
little is exons
Nucleolus
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A double membrane with pores encloses
the nucleus
The nucleolus (plural nucleoli) is a "sub-organelle" of the
nucleus. A main function of the nucleolus is the
production and assembly of ribosome components
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Mitochondria
membranebound!
(Wikipedia)
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Hydrogenosomes
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Physiology of the hydrogenosome
(Brock)
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(fully understood?)
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Chloroplasts
● Same (homolog) structure as mitochondrion, ribosomes, DNA
● Different names (compare also with bacterial cell!)
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Endoplasmic reticulum (ER)
● Rough ER -> production of
(glyco-) proteins
● Smooth ER -> production of
lipids, carbohydrates
(Wikipedia)
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Golgi complex
• Closely associated with ER
(transitional vesicles)
• Asymmetric (cis-, trans-site)
• Modification of proteins (glycosilation,
activation by limited proteolysis)
• Sorting of degradative enzymes
(lysosomes), secretory enzymes
(exoenzymes)
• Secretion
• Regeneration of the cell membrane
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Phagocytosis and pinocytosis
● Incorporation (and release) of particular or liquid structures
into membrane vesicles (food vacuoles)
● Uptake of compounds into the cytoplasm requires osmotrophic processes
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Lysosomes and peroxisomes
● Lysosomes -> production of digestive enzymes
(Don't mix with lysozyme)
● Peroxisomes -> production of reactive H2O2 by incomplete O2 reduction
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Microfilaments and microtubules
From Wikipedia, the
free encyclopedia
Microfilaments (fluorescence
after staining with phalloidin)
Microtubule structure
● Forming cytoskeleton
● Microfilaments 8 nm thick, protein: actin
● Microtubules 25 nm thick, protein: tubulin
● Homologs in prokaryotes: proteins MreB and FtsZ
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Flagella and cilia
500 nm
Prokaryotic flagellum (Brock)
Eukaryotic flagella (Cross section, Wikipedia)
● Eukaryotic flagella long, cilia short
● Complex (9 + 2) structure, proteins: tubulin + dynein (= ATPase)
● Not rotating, ATP-consuming movement includes sliding of the central
(axoneme) filaments against one another
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Life cycle of yeast
(Saccharomyces)
● Eukaryotes can have haploid and diploid cells, males
and females, and sex
● Cell division normally occurs via mitosis, the transition from dipoloid to haploid
involves meiosis
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Differences between Bacteria, Archaea and Eukarya
Compartments
separated by
membranes
Bacteria
Archaea
Eukarya
No (rare)
No (rare)
Nuclear membrane
mitochondria, chloroplasts,
endoplasmic reticulum,
membrane vesicles, vacuoles
≈1 µm
≈20 µm
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Several
Some: vacuoles or
gas vacuoles (protein)
Some: endospores
Size
Chromosome
≈1 µm
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(often plasmids)
Sexual
reproduction
Ribosomes
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No
No
(Conjugation, partial transfer
of DNA possible)
70 S
Meiosis
70 S
80 S
Flagella
Simple
Simple
Composed (9+2) structure
Cell wall
Murein
Proteins, polysaccharides,
pseudomurein etc.
Cellulose, carbonates,
silicate etc.
Membranes
contain
Hopanoids
Ether lipids
Steroids
© Heribert Cypionka, www.icbm.de/pmbio
Suggestions for homework
● Repeat the steps of mitosis, meiosis and the
eukaryotic cell cycle
● Come to my office – let's start a hay infusion
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