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Chapter 3

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Chapter 3. Functional Anatomy of Prokaryotic and Eukaryotic Cells. Prokaryotes can be grouped based on morphology Genetically determined Monomorphic vs pleomorphic Size Range 0.2 to 80 um in diameter 2 to 600 um in length Average size: 0.2 -1.0 µm × 2 - 8 µm.

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Chapter 3

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  1. Chapter 3 Functional Anatomy of Prokaryotic and Eukaryotic Cells

  2. Prokaryotes can be grouped based on morphology • Genetically determined • Monomorphic vs pleomorphic • Size Range • 0.2 to 80 um in diameter • 2 to 600 um in length • Average size: 0.2 -1.0 µm × 2 - 8 µm

  3. Morphology of Prokaryotic Cells • Prokaryotes exhibit a variety of shapes • Most common

  4. Spiral

  5. Uncommon Shapes Stella Haloarcula

  6. Cells may form groupings • Cells adhere together after division • Form characteristic arrangements • Depends on plan of division

  7. Neisseria • Enterococcus Micrococcus Sarcina Staphylococcus aureus

  8. Bacillus anthracis • Bacillus megaterium • Bordetella pertussis

  9. Layers External to Cell Wall • Glycocalyx • Made inside the cell; excreted to surface • General functions • Protection • Attachment • Motility

  10. Capsule or Slime Layer • Chemical composition varies depending on species

  11. Flagella • Naked filaments composed of flagellin • Rotate clockwise/counterclockwise • Runs and tumbles • Taxis

  12. Flagella structure has three basic parts • Filament • Hook • Basal body

  13. Polar - Monotrichous Polar -Lophotrichous Peritrichous Polar -amphitrichous

  14. Axial filaments • Bundles of endoflagella that spiral around cell • Spirochete bacteria only • Corkscrew motion

  15. Attachment Proteins • Fimbriae - bacteria • Filaments of pilinprotein • Attachment • Hami – archaea • Hooked protein filament • Attachment • Sex Pili • Pilin tubules • Exchange of DNA

  16. Cannulae – thermophilic archaea Spinae- marine bacteria Connect cells over distances Creates mesh-like network

  17. Prokaryotic Cell Wall • Determines shape of cell • Protects from osmotic pressure • Anchor point for flagella • Contributes to virulence

  18. Unique chemical structure • Bacteria vs. Archaea • Gram positive vs. Gram-negative • Peptidoglycan (PTG) (murein) • Sugar found only in bacteria • Archaea may have proteins or alternate sugars

  19. Basic structure of PTG • Disaccharide polymer • N-acetylglucosamin (NAG) • N-acetylmuramic acid (NAM) • Glycan chain held together by amino acids • Tetrapeptide chain • Protein crossbridges may or may not be present • Mostly G+

  20. Gram positive cell wall • Thick layer of PTG • Teichoic acids • Lipoteichoic or Wall teichoic acids • Polyalcohols that provide antigenic specificity • May have external protein or sugar layer

  21. Gram-negative cell wall • Little or no PTG • Outer lipopolysaccharide membrane (LPS) • O-specific polysaccharide side chain • Lipid A endotoxin • Significant periplasmic space

  22. GRAM STAINING • Gram-positive and gram-negative bacteria can be identified using a “gram stain”

  23. Summary of Gram + vs. Gram – • G+ cell • many rigid layers of peptidoglycan • teichoic acids • No outer LPS membrane • 2 ring basal body anchoring flagella • G- cell • Little or no peptidoglycan • no teichoic acids • LPS outer membrane • 4 ring basal body anchoring flagella

  24. Atypical cell wall • Acid-fast cell walls • Classified as gram-positive • mycolic acid bound to PTG • Mycobacterium • Nocardia

  25. Chlamydia • Classified as Gram – with no PTG • cysteine-rich proteins

  26. No cell wall • Mycoplasmas • Sterols in plasma membrane

  27. Structures Internal to Cell Wall • Cytoplasmic membrane • Delicate thin fluid structure • Defines boundary • Serves as a semi permeable barrier

  28. Fluid mosaic model • Phospholipid Bilayer • Amphipathic

  29. Embedded with numerous proteins • receptors , transport, enzymes • Prokaryotes typicallydon’t have membrane sterols • Bacteria may have hopanoids

  30. Photosynthetic pigments on in-foldings • chromatophores or thylakoids

  31. Archaea have distinct membrane lipids • Ether linkage • Diether or tetraether • Glycerol group enantiomer • Branched isoprenoid sidechain • May form mono-layer with greater rigidity

  32. Top: archaeal phospholipid, 1 isoprene sidechain, 2 ether linkage, 3 L-glycerol, 4 phosphate group Middle:bacterial and eukaryotic phospholipid: 5 fatty acid, 6 ester linkage, 7 D-glycerol, 8 phosphate group Bottom: 9 lipid bilayer of bacteria and eukaryotes, 10 lipid monolayer of some archaea.

  33. Membrane is selectively permeable • Few molecules pass through freely • Movement involves both active and passive processes

  34. passive processes • no energy (ATP) required • Along gradient • simple diffusion, facilitated diffusion, osmosis

  35. Simple diffusion • Facilitated diffusion

  36. Osmosis • Osmotic pressure

  37. active processes • energy (ATP) required • Active transport

  38. Group translocation • Phosphotransferase system • PEP group translocation PEP transferase animation

  39. Internal Structures • Structures essential for life • Chromosome • Ribosome • Optional but may provide selective advantage • Cytoskeleton • Plasmid • Storage granules • Endospores

  40. Internal Structures • Primary Chromosome • Resides in nucleoid • Typically single circular chromosome • Archaea - histone proteins • Bacteria - condensinprotiens • Asexual reproduction • Binary fission, budding, fragmenting, spores

  41. Plasmids • Small DNA molecules • replicated independently • nonessential information • used in genetic engineering biotechnology

  42. Ribosomes (70S) • Composed of large and small subunits • made of riboprotein and ribosomal RNA • differ in density from eukaryotic ribosomes

  43. Inclusions • Metachromatic granules • Polysaccharide granules • lipid inclusions • sulfur granules • carboxyzomes • magnetosomes • Gas vesicles

  44. Endospores • “Resting cells” • Highly resistant • Heat, desiccation, chemicals and UV light • Not reproduction! Endospore producers include Clostridium and Bacillus

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