intro08 - "The fundamental differences in the...

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2 PROKARYOTES VS. EUKARYOTES Cell Structure: Prokaryotic Eukaryotic Organization Unicellular Unicellular/ Multicellular Cell Membrane: transport, motility, transport oxidative phosphorylation, DNA replication Endocytosis/Exocytosis - + Intracellular Membranes: - + Nucleus, Golgi, Mitochondria, Endoplasmic Reticulum Cytoskeletal: Microfilaments - + Microtubules - + Cell wall Peptidoglycan - Genetics: Chromosomes 1 >1 Topology Circular Linear Segregation Cell membrane Mitotic spindle Transcription/ coupled in Transcription - nucleus Translation cytoplasm Translation - cytoplasm mRNA capping, - + poly-A Introns (-) + Cistron structure Polycistronic Monocistronic Ribosome 70S (50S + 30S) 80S (60S + 40S) Genetic Transformation, Meiosis, Zygote fusion Exchange Transduction, Conjugation "The fundamental differences in the structure and physiology of bacteria as infectious agents vs. us as hosts are the bases for most of the damaging effects of infectious disease and our ability to fight infectious disease with antibiotics." For example, the small size and simple internal structure enable the rapid growth of bacteria to contaminate food or overcome host defenses.
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3 I. Bacterial structure A. Bacteria are small (1-8 μ M) B. Primary shapes (important for identification and making diagnosis) 1. Rods 2. Cocci 3. Spirochetes 4. Others (vibrios, filamentous, coccobacilli) C. Envelope structure is unique to prokaryotes 1. Cell wall - rigid structure surrounding the cell membrane a. functions - prevent osmotic lysis, protect cell from external stresses (host), contributes to virulence, target for antimicrobials b. characterized by the Gram stain and Acid fast stain i. gram-positive ii. gram-negative iii. acid fast iv. wall-less 2. Gram-positive structure - a. thick peptidoglycan cell wall (40+ layers of chain link fence) b. thick peptidoglycan enables cell to resist lysis by complement, but still can be opsonized c. teichoic acids and lipoteichoic acids (polymer of ribitol or glycerol - phosphates) d. other proteins and carbohydrates (e.g., M protein fibrillar layer and Group A carbohydrate capsule of Streptococcus pyogenes contribute to virulence).
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4 3. Gram-negative structure - a. the outer membrane - a second lipid bilayer b. periplasmic space between inner (cytoplasmic) and outer membrane c. single layer of peptidoglycan in periplasmic space d. special outer membrane proteins ( porins ) enable diffusion across outer membrane e. outer surface of the outer membrane contains unique lipid component - lipopolysaccharide (LPS) , which is extremely important in pathogenesis
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5 D. Peptidoglycan = murein layer 1. unique to prokaryotes a. target of antimicrobials - β - lactams: penicillins and cephalosporins, vancomycin, bacitracin b. the host enzyme lysozyme in tears, etc., hydrolyses peptidoglycan backbone 2. composition - murein backbone with unusual peptide chain a. N-acetyl glucosamine - N-acetyl muramic acid b. pentapeptide with L and D amino acids 3. synthesis a. build blocks in cytoplasm
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intro08 - "The fundamental differences in the...

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