bio- chap 27

bio- chap 27 - I Prokaryotic World A outnumber eukaryotes...

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A. outnumber eukaryotes- dominate biosphere B. small and pervasivE C. bacteria and archaea are two main branches of prokayote evolution 1. in 5 kindgom system- prokaryotes are monera 2. due to genetic information, scientists determined that prokaryotes comprised bacteria and archaea (inhabitants of extreme environments) a. proposed 6 kingdom system: 2 prokaryotic kingdoms in addition to the 4 eukaryotic kingdoms b. favor idea of 3 domains- prokaryotes are domain bacteria and domain archaea II. Structure, Function, and reproduction of Prokaryotes A. most unicellular with occasional simple multicellular organization B. shapes: spheres (cocci), rods (bacilli) and helices (including spirilla and spirochetes) C. majority have 1-5 um diameter, with some exceptions D. Cell Walls 1. external to plasma membranes 2. maintain cell shape 3. physical protection 4. prevents cell from bursting in a hypotonic environment (prokaryotes plasmolyze in hypertonic medium) 5. walls composed of peptidoglycan a. polymers of modified sugars crosslinked by short polypeptides that vary from species to species b. effect: single molecular network enclosing and protecting cell 6. Gram Stain: used to separate many membrs of domain Bacteria into 2 grps based on differences in cell walls a. gram positive: simpler walls, with large amnt of peptidoglycan b. gram negative: less peptidogylcan, more complex. Out memb on cell wall contains lipopolysaccharide. More threatening pathogenically than gram +. 7. capsule: sticky substance secreted to form a protectve layer outside the wall that enable orgs. to adhere to their substrate and provide additional protection- resistance of pathogenic prokaryotes to host defenses 8. pili/pilus also allows cell to stick to each other E. Motility 1. capable of directional movement 2. flagellar action is most common a. scattered all over cell surface b. or concentrated in areas c. 1/10 width of eukaryotic flagella and are not covered by an extension of the plasma memb. 3.
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bio- chap 27 - I Prokaryotic World A outnumber eukaryotes...

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