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Transcript
Bacterial and Cellular Structures Chapter 3 Objectives for today • Understand the function of a variety cellular structures • The uses of the cell membrane • Overview of some differences between prokaryotes and eukaryotes – Important for medical targets! Definitions Poly = Many, Mono = 1, Di = 2, Tri = 3 • Polysaccharide Sugar • Lipid/phospholipid – Non-polar, hydrophobic molecule comprising the cell membrane • ATP (Adenosine Triphosphate) – The energy containing molecule Bacterial Structures Capsule or Glycocalyx • Outermost layer • Polysaccharide or polypeptide • Allows cells to adhere to a surface • Contributes to bacterial virulence-avoid phagocytosis Filamentous Protein Appendages Flagella - motility Rotate like a propeller Proton motive force used for energy Presence/arrangement can be used as an identifying marker Flagella - motility Rotate like a propeller Proton motive force used for energy Presence/arrangement can be used as an identifying marker Peritrichous Polar Other (ex. tuft on both ends) Flagella - motility Chemotaxis - Directed movement towards/away from a chemical •Cell movement is due to a series of “runs” and “tumbles” •“Runs” are longer when cell is going in the right direction https://www.youtube.com/watch?v=EpC6G_DGqkI Different types of pili Common pili (fimbriae) Sex pili - Conjugation Cell Wall Provides rigidity to the cell •Protection against osmotic forces • Bursting from massive influx of water Cell Wall Provides rigidity to the cell (prevents it from bursting) Cell Wall •Peptidoglycan - rigid molecule; unique to bacteria •Alternating subunits of NAG and NAM form glycan chains •Glycan chains are connected to each other via peptide chains on NAM molecules Cell Wall Cell Wall •Peptidoglycan - rigid molecule; unique to bacteria •Alternating subunits of NAG and NAM form glycan chains •Glycan chains are connected to each other via peptide chains on NAM molecules Medical significance of peptidoglycan •Target for selective toxicity; synthesis is targeted by certain antimicrobial medications (penicillins, cephalosporins) •Recognized by innate immune system •Target of lysozyme (in egg whites, tears) Cell Wall Gram-positive Thick layer of peptidoglycan Teichoic acids Cell Wall Gram-negative Thin layer of peptidoglycan Outer membrane - additional membrane barrier; porins permit passage lipopolysaccharide (LPS) Cell Wall Gram-negative Thin layer of peptidoglycan Outer membrane - additional membrane barrier; porins permit passage lipopolysaccharide (LPS) - ex. E. coli O157:H7 endotoxin - recognized by innate immune system Cell Wall Gram-negative Thin layer of peptidoglycan Outer membrane - additional membrane barrier; porins permit passage lipopolysaccharide (LPS) periplasm Cytoplasmic membrane •Defines the boundary of the cell •Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules •Transport proteins function as selective gates (selectively permeable) •Control entrance/expulsion of antimicrobial drugs •Receptors provide a sensor system •Phospholipid bilayer, embedded with proteins Cytoplasmic membrane •Defines the boundary of the cell •Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules •Transport proteins function as selective gates (selectively permeable) •Control entrance/expulsion of antimicrobial drugs •Receptors provide a sensor system •Phospholipid bilayer, embedded with proteins Cytoplasmic membrane •Defines the boundary of the cell •Semi-permeable; excludes all but water, gases, and some small hydrophobic molecules •Transport proteins function as selective gates (selectively permeable) •Control entrance/expulsion of antimicrobial drugs •Receptors provide a sensor system •Phospholipid bilayer, embedded with proteins •Fluid mosaic model Cytoplasmic membrane Electron transport chain - Series of proteins that eject protons from the cell, creating an electrochemical gradient Proton motive force is used to fuel: •Synthesis of ATP (the cell’s energy currency) •Rotation of flagella (motility) •One form of transport If a function of the cell membrane is transport….. • How is material transported in/out of the cell? – Passive transport • No ATP • Along concentration gradient – Active transport • Requires ATP • Against concentration gradient Types of transport • Passive transport • Simple diffusion • Facilitated diffusion • Osmosis • Active transport • System that uses proton motive force • System that uses ATP • Group translocation Permeability of the membrane Osmosis http://www.dnatube.com/video/2775/Onion-Cells-Plasmolysis Facilitated Diffusion https://www.youtube.com/watch?v=I4123hUU8xo Active Transport Internal structures: Chromosome Internal structures: Ribosomes https://www.youtube.com/watch?v=hEtONGf4Z0A Internal structures:Storage Granules Internal Structures: Endospores Eukaryotes • Larger than prokaryotes – 600uM vs 10uM • Nucleated • Many organelles not found in prokaryotes – ER, golgi, mitochondria, etc Encyclopedia of worlds, David Darling Plant Cells • Eukaryote • Photosynthesis in chloroplasts • Cellulose cell walls Mitochondria (all eukaryotic cells) Chloroplasts (plant cells only)
