Chapter 4a - Chapter 4 Functional Anatomy of Prokaryotic...

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Unformatted text preview: Chapter 4 Functional Anatomy of Prokaryotic and Eukaryotic Cells Bacteria can be classified based on size, morphology and arrangement Size 0.2 to 2.0 um in diameter 2 to 8 um in length Size in the Microbial World Morphology of Prokaryotic Cells Prokaryotes exhibit a variety of shapes Most common Coccus Bacillus Other shapes Coccobacillus Vibrio Spirillum Spirochete Prokaryotic cells may form groupings after cell division Cells adhere together after cell division for characteristic arrangements Arrangement Especially depends on plan of division in the cocci Diplococci - Neisseria Streptococci - Streptococcus Sarcina Staphylococcus Uncommon Shapes Shape is genetically determined most are monomorphic some are pleomorphic Layers External to Cell Wall Glycocalyx Made sugar coat inside the cell; excreted to surface General functions Protection Protects bacteria from host defenses and desiccation bacteria to adhere to specific surfaces Attachment Enables Glycocalyx Chemical arrangements Capsule or Slime Layer composition of capsules and slime layers varies depending on bacterial species Flagella Long filamentous appendages composed of simple protein Rotate clockwise or counterclockwise runs and tumbles Taxis (chemo, photo, aero) Flagella structure has three basic parts Filament Hook Basal body Polar - Monotrichous Polar -Lophotrichous Peritrichous Polar -amphitrichous Axial filaments Bundles of fibers that spiral around cell only Spirochetes Corkscrew motion Pili Consist occur of pilin protein Fimbriae all over the cell from a few to several hundred per cell Sex pilus Longer, few per cell used to join bacteria for exchange of DNA Prokaryotic Cell Wall Rigid structure Surrounds cytoplasmic membrane Determines shape of cell Prevents cell from bursting Anchor point for flagella Contributes to pathogeneses Site of action for some antibiotics Unique chemical structure Distinguishes Gram positive from Gram-negative bacteria and archaea bacterial species Rigidity of cell wall is due to peptidoglycan (PTG) Compound found only in bacteria Archaea psudomurein Many antimicrobial interfere with synthesis of PTG Lysozyme Penicillin; Basic structure of peptidoglycan series of two subunits Alternating N-acetylglucosamin (NAG) N-acetylmuramic acid (NAM) Joined subunits form glycan chain Glycan chains held together by string of four amino acids Tetrapeptide chain Gram positive cell wall thick layer of many as 30 Relatively PTG As Teichoic acid component of PTG Gram-negative cell wall Only contains thin layer of PTG sandwiched between outer membrane and cytoplasmic membrane called periplasm Region Outer membrane of lipid bilayer called the lipopolysaccharide or LPS layer Constructed also LPS severs as barrier to a large number of molecules Small molecules or ions pass through channels called porins Resistant to many antibiotics Portions of LPS medically significant polysaccharide side chain to identify certain species or strains may play role in recognition of infection O-specific Used Lipid A Toxin, Differences between Gram + and Gram cell walls G+ cell many layers of peptidoglycan contain teichoic acids thick rigid structure G- cell no teichoic acids few layers of peptidoglycan LPS outer membrane Lysozymes Enzyme tears produced in many body fluids and saliva Breaks Often bond linking NAG and NAM structural integrity of cell wall Destroys used in laboratory to remove PTG layer from bacteria Produces protoplast in G+ bacteria Produces spheroplast in G- bacteria Some bacteria have an atypical cell wall Mycobacterium Causes leprosy mycolic acids tuberculosis and Some bacteria naturally lack cell wall Mycoplasma Bacterium causes mild pneumonia Sterols in membrane account for strength of membrane Structures Internal to Cell Wall Cytoplasmic Delicate membrane thin fluid structure Surrounds cytoplasm of cell Defines boundary Serves as a semi permeable barrier Barrier between cell and external environment Fluid mosaic model Phospholipid contains Bilayer a hydrophilic phosphate head and hydrophobic fatty acid tail Membrane Function is embedded with numerous protein as receptors and transport gates Provides mechanism to sense surroundings Enzymes catalyze chemical reactions Photosynthesis Energy production Cytoplasmic membrane is selectively which molecules pass into or out permeable Determines of cell Few molecules pass through freely Movement involves both active and passive processes passive no processes energy (ATP) required Along gradient simple diffusion, facilitated diffusion and osmosis Simple diffusion Facilitated diffusion Can only eliminate concentration gradient it cannot create one Osmosis Osmotic pressure Isotonic Hypotonic Hypertonic active processes (ATP) required energy Against gradient Active transport Group translocation Phosphorylates molecule during transport Internal Structures Bacterial cells have variety of internal structures Some structures are essential for life Chromosome Ribosome Others are optional and can provide selective advantage Plasmid Storage granules Endospores Internal Structures Primary In Chromosome in cytoplasm Resides nucleoid space Typically single chromosome Circular double-stranded molecule Contains all genetic information Asexual reproduction Binary fission, budding, fragmenting Plasmids small, circular, double-stranded DNA molecules replicated independently nonessential information used in genetic engineering biotechnology Ribosomes Involved in protein synthesis Composed of large and small subunits Units made of riboprotein and ribosomal RNA differ from eukaryotic ribosomes Difference often used as target for antimicrobials Storage granules Metachromatic granules Polysaccharide granules lipid inclusions sulfur granules carboxyzomes magnetosomes Gas vesicles Endospores Dormant In cell types response to poor environmental conditions Resistant Heat, to damaging conditions desiccation, chemicals and UV light Important in food/ medicine Vegetative cell produced through germination a source of reproduction Common bacteria genus that produce endospores include Clostridium and Bacillus Not Fig. 4.21 ...
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This note was uploaded on 02/21/2008 for the course BIOLOGY 380 taught by Professor Littlejohn during the Spring '06 term at University Of Southern Mississippi .

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