Transcript “Anatomy” and Function of Prokaryotes I

“Anatomy” and Function of
Prokaryotes I
• Cell Size Shape and Arrangement
• Prokaryote “Anatomy” Overview
• Cytoplasmic Matrix and Structures
• Membranes (plasma; outer; internal)
Cell Shape and Arrangement
Cell Shape and Arrangement
star
rectangle
pleomorphic = irregular
hypha = thin tubes
prosthecate = appendage
Multicellular Organization?
Not every cell is alike; nor just members of a colony.
Bacillus subtilis
Proteus mirabilis
Myxobacterium sp.
Prokaryote
“Anatomy”
Overview
Cell envelope: Collectively all the structures
outside from the plasma membrane.
Cytoplasmic Matrix and Structures
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Cytoplasmic proteins
Ribosomes
Nucleoid
Inclusion Bodies
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Glycogen (C)
Poly-β-hydroxybuterate (C)
Cyanophycin (N) granules
Carboxysomes (RuBPcase)
Gas vacuoles (vesicles)
Polyphosphate granules
Sulfur granules
Magnetosomes
Fig 3.10
Inclusion Bodies
Gas Vacule = buoyancy
Magnetosomes = orientation
(freeze fracture SEM)
(TEM)
Ribosomes
• Subunits made of proteins and ribosomal ribonucleic acids (rRNA).
• 30S and 50S must bind together to form a complete and functional ribosome.
• The two subunits “sandwich” messenger RNA (mRNA).
• As it moves along the mRNA, the genetic code is “translated” into a
polypeptide by the directed polymerization of amino acids.
• Transfer RNAs (tRNA) shuttle the amino acids to the ribosome as needed.
• Hence, ribosomes are responsible for protein synthesis.
Nucleoid
• The compact form of
the bacterial circular
chromosome (0.5 to 5
Mega base pairs (Mbp).
• DNA supercoils
forming ~ 60 loops.
• Histone-like proteins
centrally anchor loops.
• Active growing cells
may have >1 nucleoid;
loops uncoil and extend
for gene expression.
Plasma Membrane
• Membrane lipids are amphipathic.
• Membranes are lipid bilayers (hydrophilic outside
and hydrophobic inside)
• Stabilized by hopanoids &
long-chain saturated fatty acids.
• Functions:
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Selective permeable bearer into (out of) cytoplasm.
Transport for nutrients, excretion, secretion
Sensing the environment & signaling a response
Metabolic processes (respiration; photosynthesis …)
Secretion
Plasma
Membranes
Internal Membranes
• Invagination of plasma membrane.
• Shaped into vesicles, tubules, or lamellae.
• “mesosomes” are small; simple; unknown function (possibly
chromosome replication)
• Photosynthetic and Nitrifying bacteria have complex folded lamellae;
increase surface area for certain metabolic.