Prokaryotic cells structure and function

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Prokaryotic cells structure and function
2014-07-09 03:25:03

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  1. features of prokaryotes that are different from eukaryotes
    • do not have a membrane surrounding DNA
    • Lack various internal structures
    • are smaller
    • 70s ribosomes
  2. features of eukaryotes that are different from prokaryotes
    • membrane bound nucleus
    • have organelles such as the mitochondria and chloroplasts
    • larger in size
    • 80s ribosomes
  3. how large are the 2 subunits of ribosomes for prokaryotes?
    30s and 50s
  4. how large are the 2 subunits of ribosomes for eukaryotes?
    60s and 40s
  5. what is s (svedberg units)?
    • give a measure of sedimentation velocity (rate at which a particle sediments in a tube under centrifugal force)
    • the faster a particle travels when centrifuged, the greater its svedberg value
  6. what are the most common shapes of bacteria?
    rods and cocci (spheres)
  7. what is a tetrad?
    4 cocci grouped together in the same plane
  8. how big are nanobacteria?
    less than .2micrometers
  9. what is the average size of a bacteria?
    • 1-2 micrometers in width
    • 2-10 micrometers in height
  10. what is a sarcinae?
    8 cocci gouged together in a box shape
  11. what is a bacilli?
    a rod shape of bacteria
  12. what is a spirilla?
    rigid helices shape of bacteria
  13. what is spirochetes?
    flexible helices shape of bacteria
  14. why might it be advantageous to have a small size for bacteria?
    • may be protection mechanism from predation
    • gives a larger surface area to volume ratio which is important for nutrient uptake
  15. what are the functions of the plasma membrane?
    • encompasses the cytoplasm
    • selectively permeable barrier
    • interacts with external environment (receptors, transport, metabolic processes)
  16. what are the sterol like molecules in bacterial membranes?
  17. what are growth factors?
    organic compounds that must be provided by the environment if the cell is to survive and reproduce
  18. what are the classes of growth factors?
    • amino acids
    • purines and prymidines
    • vitamines
    • heme
  19. what is the use of amino acids for bacteria?
    building blocks for protein synthesis
  20. what is the use of purines and pyrimidines for bacteria?
    building blocks for nucleic acid synthesis
  21. what is the use of vitamins for bacteria?
    function as enzyme cofactors
  22. what is the use of heme in bacteria?
    functions in cytochromes of electron transport chains
  23. which transport mechanism is used in eukarya only?
  24. what are the transport mechanisms used by microorganisms?
    • facilitated diffusion
    • active transport
    • group translocation
    • endocytosis
  25. what is the difference between facilitated diffusion and passive diffusion?
    facilitated diffusion uses membrane bound carrier molecules
  26. what sort of molecules are transported using facilitated diffusion?
    glycerol, sugars, amino acids
  27. what is active transport?
    • energy dependent process to move molecules against the concentration gradient
    • it involves carrier proteins
  28. what is the mechanism of action of ABC transporters?
    • solute binds to the solute-binding protein and approaches the ABC transporter
    • the solute binding protein attaches to the ABC transporter
    • hydrolysis of ATP drives movement of solute across membrane
  29. what is group translocation?
    energy dependent transport that chemically modifies molecule as it is brought into the cell
  30. how do microorganisms uptake iron?
    microorganisms secrete siderophores to complex with ferric ion and aid uptake
  31. how are peptidoglycan chains strengthened?
    by cross linking
  32. where is the periplamic space of gram positive?
    lies between the plasma membrane and the cell wall
  33. what are exoenzymes?
    enzymes secreted by gram positive bacteria that aid in the degradation of large nutrients
  34. what is the structure of cell wall in gram positive bacteria?
    • thick layer of peptidogycan
    • periplamic space
    • then cell wall
  35. what is the structure of cell wall in gram negative bacteria?
    • consists of a thin layer of peptidoglycan surrounded by and outer membrane
    • outer membrane composed of lipids, lipoproteins and lipopolysaccharides
    • no teichoic acids
  36. what are the 3 parts of lipopolysaccharides?
    • lipid A
    • core polysaccharide
    • O side chain
  37. where is lipid A imbedded in the lipopolysaccharide?
    embedded in the outer membrane
  38. which parts of the lipopolysaccharide extend out from the cell?
    the core polysaccharide and the O side chain
  39. why is the LPS important?
    • contribues to negaitve charge on cell surface
    • helps to stabilize outer membrane structure
    • may contribute to attachment to surfaces and biofilm formation
    • creates a permeability barrier
    • protection from host defenses (O antigen)
    • can act as an endotoxin (Lipid A)
  40. why is the outer membrane of gram negative more permeable than plasma membranes?
    presence of porin proteins and transporter proteins
  41. what is the gram reaction color for gram positive?
  42. what is the gram reaction color for gram negative?
  43. what is the effect of iodine on gram +?
    dye trapped in wall
  44. what is the effect of iodine on gram -?
    nothing happens, purple dye stays on cell walls
  45. what is the effect of alcohol on gram +?
    crystals remain on cell wall
  46. what is the effect of alcohol on gram -?
    outer membrane is weakened and the wall loses the dye
  47. what is the effect of the red dye (safranin) on the gram +?
    red dye masked by violet
  48. what is the effect of the red dye (safranin) on the gram -?
    red dye stains the colorless cell
  49. what is the outermost layer in the cell envelope made of?
    • glycocalyx
    • (capsules and slime layers/ s layers)
  50. what does the glycocalyx do?
    aid in the attachment to solid surfaces
  51. what are the protective advantages of capsules?
    • resistant to phagocytosis
    • protect from desiccation
    • exclude viruses and detergents
  52. what are the function of S layers?
    • protect from ion and pH fluctuations
    • promotes adhesion to surfaces
    • protects from host defenses
    • potential use in nanotechnology b/c S layer spontaneously forms
  53. what are the bacterial cytoplamic structures?
    • cytoskeleton
    • inclusion
    • ribosomes
    • nucleoid and plasmids
  54. what is a plasmid?
    extrachromosomal DNA that exist independently of chromosomes
  55. how can plasmids be transferred between bacteria?
  56. what are R plasmids?
    genes that carry antibiotic resistance
  57. what are fimbriae?
    short thin hairlike appendages that can mediate attachment to surfaces for motility or DNA uptake
  58. what is sex pili?
    longer thicker and less numerous appendages that are required for conjugation
  59. that are flagella
    Threadlike, locomotor appendages extending outward from the plasma membrane and cell wall
  60. what are the function of flagella?
    • -motility and swarming behavior
    • – attachment to surfaces
    • – may be virulence factors
  61. what are the 3 parts of the flagella and what do they do?
    • 1. filament - extends from cell surface to the tip, made of hollo rigid cylinder of flagellin protein
    • 2. hook - links filament to basal body
    • 3. basal body - series of rings that drive flagellar motor
  62. what is a bacterial endospore?
    a complex dormant structure formed by some bacteria that is resistant to numerous environmental conditions
  63. what makes an endospore resistant?
    • calcium complexed with dipicolinic acid
    • small acid soluble DNA binding proteins
    • dehydrated core
    • spore coat and exosporium protect it
  64. when does sporulation occur?
    normally commences when growth ceases because of pact of nutrients