Download Procaryotic cell

STRUCTURE OF
PROCARYOTIC CELL
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SIGNIFICANCE OF PROCARYOTIC CELL
STRUCTURE IN MEDICINE
Example:
• Procaryotic cells: pathogenic bacteria (e.g. Mycobacterium
tuberculosis, Vibrio choleare)
• Possibility of the therapy of bacterial diseases: antibiotics
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STRUCTURE OF PROCARYOTIC CELL
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Basic structure of procaryotic cell
Nucleoid
Plasmids
Cytoplasm
Plasma membrane
Cell wall
Flagella
Size and morphology of procaryotic cells
Metabolism of procaryotic cells
Bacteria and archaea
Comparison of procaryotic and eucaryotic cell
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1. BASIC STRUCTURE OF PROCARYOTIC
CELL:
• Procaryotic cell (procaryotes): chromosomal DNA is not bounded
by membrane, i.e. the cell has not regular nucleus.
• Eucaryotic cell (eucaryotes): chromosomal DNA is bounded by
membrane, i.e. the cell has regular nucleus.
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Basic structure of procaryotic cell:
• nucleoid (DNA)
• cytoplasm
• plasma membrane & cell wall
Some procaryotic cells have flagellum.
Procaryotic cells do not contain membrane-bounded organelles
(mitochondria, chloroplasts etc.)!
[FIG.]
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2. NUCLEOID:
It contains one molecule of doublestranded (ds) DNA (procaryotic
chromosome) and proteins.
→ Procaryotic cell is haploid.
• Procaryotic chromosome: mostly circular, arranged in the form of
loops and attached to plasma membrane.
Proteins: HLP (histone like protein) proteins and other proteins.
Procaryotic chromosome involves about 1000 - 4000 genes.
Procaryotic chromosome contains all genes indispensable for the life
of procaryotic cell.
Whole procaryotic chromosome functions as a replicon, i.e. it has one
replication origin (oriC in the case of E. coli). The chromosome is
attached to plasma membrane by replication origin.
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3. PLASMIDS:
Plasmid represents a small circular doublestranded DNA. It involves
genes which are not indispensable for the life of procaryotic cell.
• F plasmid: genes indispensable for conjugation
• R plasmids: genes producing resistance to antibiotics etc.
[FIG.] [FIG.]
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4. CYTOPLASM:
Cytoplasm is without cytoskeleton and mostly without organelles.
• Ribosomes (70s): 5S-rRNA, 16S-rRNA, 23S-rRNA
[FIG.]
DNA replication and DNA transcription as well as mRNA translation are
realized in cytoplasm.
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4. CYTOPLASM:
Cytoplasm is without cytoskeleton and mostly without organelles.
• Ribosomes (70s): 5S-rRNA, 16S-rRNA, 23S-rRNA
[FIG.]
DNA replication and DNA transcription as well as mRNA translation are
realized in cytoplasm.
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5. PLASMA MEMBRANE:
Plasma membrane: selective barrier of the cell against outside
enviroment (procaryotes and eucaryotes)
Internal membranes of the cell: membrane-bounded organelles →
compartmentalization of cell interior (only eucaryotes)
[FIG.]
Specialized membranes of procaryotic cell: membrane invagination
(seemingly internal)
[FIG.]
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5. PLASMA MEMBRANE:
Plasma membrane: selective barrier of the cell against outside
enviroment (procaryotes and eucaryotes)
Internal membranes of the cell: membrane-bounded organelles →
compartmentalization of cell interior (only eucaryotes)
[FIG.]
Specialized membranes of procaryotic cell: membrane invagination
(seemingly internal)
[FIG.]
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6. CELL WALL:
Most of procaryotic cells have rigid cell wall (Mycoplasma cells are the
exception). [FIG.]
Structure of cell wall: polymers of peptidoglycan (murein)
• Gram-positive bacteria: cell wall only from peptidoglycans.
• Gram-negative bacteria: cell wall is supplemented with
lipopolysaccharide coat.
[FIG.] [FIG.]
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6. CELL WALL:
Most of procaryotic cells have rigid cell wall (Mycoplasma cells are the
exception). [FIG.]
Structure of cell wall: polymers of peptidoglycan (murein)
• Gram-positive bacteria: cell wall only from peptidoglycans.
• Gram-negative bacteria: cell wall is supplemented with
lipopolysaccharide coat.
[FIG.] [FIG.]
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7. FLAGELLA:
Flagella: enable movement of procaryotic cells
Structure of procaryotic flegellum: completely different than eucaryotic
flagellum (significantly thinner, it is not covered by membrane), protein
flagellin [FIG.]
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8. SIZE AND MORPHOLOGY OF PROCARYOTIC
CELLS:
Size of procaryotic cell: usually 1-10 µm.
Generally, procaryotic cell is significantly smaller than eucaryotic cell.
Shape of procaryotic cell: spherical (cocci), rod-shaped (bacilli), spiral.
[FIG.] [FIG.]
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9. METABOLISM OF PROCARYOTIC CELL:
Procaryotes exert significantly higher variability in biochemical capabilities,
including the capability of acquiring energy, than eucaryotes.
Essential ways of acquiring energy:
• Phototrophic procaryotes: they acquire energy from sunlight
(photosynthesis).
• Chemotrophic procaryotes: they acquire energy by the oxidation of
chemicals.
• Lithotrophic procaryotes: they acquire energy by the oxidation of
inorganic chemicals (e.g. the oxidation of H2S, the oxidation of
Fe2+).
• Organotrophic procaryotes: they acquire energy by the oxidation
of organic chemicals (fermentation and oxidative phosphorylation).
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Source of carbon:
• Autotrophic procaryotes: inorganic compounds (CO2) represent a
source of carbon
• Heterotrophic procaryotes: organic compounds (glucose) represent
a source of carbon
Dependence on oxygen:
• Aerobic procaryotes: they require oxygen for their metabolism
• Anaerobic procaryotes: they require the absence of oxygen for their
metabolism
Regarding their capabilities, procaryotes are capable of living even
under extreme conditions, including conditions seemingly incompatible
with life.
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10. BACTERIA AND ARCHAEA:
There are two basic groups of procaryotic organisms: bacteria, archaea
Bacteria:
Archaea:
• chromosonal DNA is not
organized in structures similar
to nucleosomes
• chromosonal DNA is organized
in structures similar to
nucleosomes
• genes without introns
• tRNA and rRNA genes contain
introns
• cell wall from peptidoglycan
• cell wall from
pseudopeptidoglycan
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Archaea often live under extreme conditions (hot springs, the depths of
oceans etc.). [FIG.]
Bacteria: Bacillus subtilis, Escherichia coli, Helicobacter pylori,
Mycobacterium tuberculosis, Mycoplasma genitalium, Treponema
pallidum
Archaea: Methanobacterium ruminantium, Methanococcus jannaschii
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Archaea often live under extreme conditions (hot springs, the depths of
oceans etc.). [FIG.]
Bacteria: Bacillus subtilis, Escherichia coli, Helicobacter pylori,
Mycobacterium tuberculosis, Mycoplasma genitalium, Treponema
pallidum
Archaea: Methanobacterium ruminantium, Methanococcus jannaschii
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11. COMPARISON OF PROCARYOTIC AND EUCARYOTIC
CELL:
Procaryotes and eucaryotes do not represent two taxonomic groups
(evolutional lines) but they represent two differing levels of cell
organization.
Procaryotic cell:
Eucaryotic cell:
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1-10 µm
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5-100 µm
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1000 - 4000 genes
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10 000 - 30 000 genes
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it does not have regular nucleus
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it has regular nucleus
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non-mitotic division of
chromosomes
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mitotic division of chromosomes
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transcription and translation are
not separated
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transcription and translation are
separated
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70S ribosomes
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80S ribosomes
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without cytoskeleton
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cytoskeleton
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without organelles
•
organelles
[FIG.] [FIG.]
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LITERATURA:
• Alberts B. et al.: Essential Cell Biology. Garland Publishing, New
York & London, pp. 11-16, 2010.
• Alberts B. et al.: Molecular Biology of the Cell. Garland Science,
New York & Abington, pp. 11-18, 2008.
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