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Published byMabel Thornton Modified over 9 years ago
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Functional Anatomy of Prokaryotic and Eukaryotic Cells
Chapter 4 Functional Anatomy of Prokaryotic and Eukaryotic Cells
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Definition of “prokaryotic”
Refers to organisms, typically 1-celled, having cells which: lack a nucleus lack membrane-bound organelles contain 1 chromosome may contain extra-chromomal DNA (plasmids) contain 70S ribosomes contain peptidoglycan cell walls
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Prokaryotic vs. Eukaryotic cells
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Bacterial cell size, shapes and arrangements
2.0 – 10.0 uM in length Eukaryotic cells ~10x larger 3 common morphologies bacillus = rod-shaped coccus = spherical shaped spirillum = spiral shaped Many arrangements diplo- strepto- Staphylo- ***spirochetes**
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Bacterial morphologies
Morphology can be used as an initial identifier However, shape can change in some bacteria depending on environs “pleomorphic” cells
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Bacterial ultrastructure
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1) Cell wall structure Alternating NAM & NAG amine sugars produce layers of block units NAM = n-acetylmuramic acid NAG = n-acetylglucosamine Layers connected by tetrapeptide chains linked to NAM’s Penta-glycine interbridges connect tetrapeptides in Gram + cells (sensitive to penicillin) Direct peptide bonds connect tetrapeptides in Gram – cells (not sensitive to penicillin) Make up peptidoglycan
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Alternating NAM-NAG with tetrapeptide connections
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Gram positive cell wall structure
Ok, not too bad – now for something completely different – Gram negative cell walls!
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Gram negative cell wall structure
Gram neg. cell walls are composed of peptidoglycan AND an outer membrane; it is multi-layered!!
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Gram negative LPS* *Lipopolysaccharide contains 3 parts:
Antigen O – can change shape in dif’t environs Core polysaccharide – contains neg. charge Lipid A – also called ‘endotoxin A’; released upon cell death and can have toxic affect on nearby cell membranes
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Gram pos. vs Gram neg cell walls
Two part structure Thin peptidoglycan (10-20 nm) Outer membrane Outer membrane contains LPS LPS imparts a negative charge Thick peptidoglycan 20-80 nm thick Retains CV-I complex of Gram stain Teichoic acid anchors cell wall to cell membrane and imparts a negative charge Glycerol-P polymer
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The Gram stain
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2) Bacterial flagella Composed of: 1) basal body, 2) filament, 3) hook
Basal body connects to cell wall and to cell membrane Uses ATP to spin
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Arrangements of flagella
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Bacteria are hampered to some extent by flagellar rotation
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