Word27 - Prokaryotes

Word27 - Prokaryotes - Chapter 27 - Prokaryotes 27.1:...

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Chapter 27 - Prokaryotes Unicellular Diameters: 1-5µm Shapes Sphere (cocci) Rods (bacilli) Spirals Cell Surface Structures **Cell Wall o physical protection o prevents cell from busting in a hypotonic environment water loss inhibits reproduction o contain peptidoglycan a network of modified-sugar polymers croo-linked by short poply peptides encloses entire bacterium anchors other molecules that extend from surface archaeal cell wall lack this but have polysaccharides & proteins
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Chapter 27 - Prokaryotes Gram stain: classifies many bacterial species into 2 groups o Gram-positive Simpler walls Large amt of peptidoglycan o Gram-negative Less peptidoglycan Structurally more complex Outer membrane: lipopolysaccharides Often toxic Protects bacteria against body’s defenses More threatening More resistant to antibiotics Certain antibiotics derives from their inhibition of the peptidoglycan cross-linking o Prevent formation of functional cell wall Covered by capsule o A sticky layer of polysaccharide / protein o Enables prokaryotes to adhere to their substrate / other individuals o Shield pathogenic prokaryotes from attacks by host’s immune system
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Chapter 27 - Prokaryotes o Hairlike appendages o Fimbriae shorter and more # o Sex pili specialized for exchange of DNA Motility ½ capable of directional movement flagella o scattered over entire surface / concentrated at one/both ends o 1/10 of eukaryotic flagella o environment uniform » may move randomly heterogeneous » many exhibit taxis movement toward / away from stimulus chemotaxis: respond to chemicals by changing movement pattern toward: positive away: negative Lack complex compartmentalization Some have specialized membranes the perform metabolic functions o Usually infoldings of plasma membrane o Aerobic prokaryote
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Chapter 27 - Prokaryotes o Photosynthetic prokaryote Cyanobacteria 1/1000 of eukaryotic DNA o ring of DNA = prokaryotic chromosome o nucleoid region: Part of cytoplasm that is lighter in microscope; where DNA is o plasmids: smaller rings of DNA consisting of only few genes provide resistance to antibiotics
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Word27 - Prokaryotes - Chapter 27 - Prokaryotes 27.1:...

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