ch 27 - BIO EXAM II ch 27 I) Prokaryotes: A) Most...

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BIO EXAM II ch 27 I) Prokaryotes: A) Most prokaryotes are unicellular B) variety of shapes, the three most common of which are spheres (cocci), rods (bacilli), and spirals C) Some prokaryotes stick to their substrate or to one another by means of hairlike appendages called fimbriae and pili D) Divide by binary fission; prokaryotic reproduction is limited, as the cells eventually exhaust their nutrient supply, poison themselves with metabolic wastes, or are consumed by other organisms E) cell walls: i) maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment ii) most bacterial cell walls contain peptidoglycan , a network of modified-sugar polymers cross-linked by short polypeptides - encloses the entire bacterium and anchors other molecules that extend from its surface iii) covered by a capsule , a sticky layer of polysaccharide or protein (a) enables prokaryotes to adhere to their substrate or to other individuals in a colony (b) can also shield pathogenic prokaryotes from attacks by their host’s immune system F) gram stain: i) Gram-positive bacteria have simpler walls with a relatively large amount of peptidoglycan ii) Gram-negative bacteria have less peptidoglycan and are structurally more complex, with an outer membrane that contains lipopolysaccharides (carbohydrates bonded to lipids) iii) inhibition of the peptidoglycan cross-linking, thus preventing the formation of a functional cell wall G) flagella i) not covered by an extension of the plasma membrane ii) motor of the prokaryotic flagellum is the basal apparatus, a system of rings embedded in the cell wall and plasma membrane iii) heterogeneous environment, however, many prokaryotes exhibit taxis , movement toward or away from a stimulus (a) prokaryotes that exhibit chemotaxis respond to chemicals by changing their movement pattern. They may move toward nutrients or oxygen (positive chemotaxis) or away from a toxic substance (negative chemotaxis)
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This note was uploaded on 04/18/2008 for the course BIOL 1308 taught by Professor Hauser during the Spring '08 term at St. Edwards.

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ch 27 - BIO EXAM II ch 27 I) Prokaryotes: A) Most...

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