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prokaryote structure and function (prokaryotic cell organisation - 3…

- - - - in actively growing cells, has projections that probably contain DNA being transcribed
        
        no membrane
      - plasmids
        
        small, closed circular DNA molecules
        
        exist and replicate independently of chromosome
        
        not required for growth and reproduction
        
        may carry genes that confer selective advantage (eg. drug resistance)
      - spores
        
        only in rod shaped bacilli (aerobes) or clostridium (anaerobes)
        
        no pores but receptors to know when to germinate
    - - structures consisting of protein and RNA, sites of protein synthesis, smaller than eukaryotic ribosomes
    - - granules of organic or inorganic material that are stockpiled by the cell for future use (like humans storing in fat)
        
        organic inclusion bodies
        
        glycogen
        
        poly-beta-hydroxybutyrate (PHB) [carbon source]
        
        gas vacuoles [bouyancy to chase nutrients]
        
        cyanophycin granules [contain amino acids]
        
        carboxysomes [photosynthetic microbes store carbon dioxide and RuBisCO enzyme]
        
        inorganic inclusion bodies
        
        polyphosphate granules [synthesize nucleic acids]
        
        sulphur granules [photosynthetic bacteria can store energy]
        
        magnetosomes (pull based on magnetic pull of earth)
      - some enclosed in a single-layered membrane (some made of proteins, some lipids)
    - - cytoskeleton
        
        actin filament - made of actin
        
        microtubules - made of tubulin
        
        intermediate filaments - mixture of different classes of proteins
  - - - encompasses cytoplasm
        
        contains lipids and proteins
        
        highly organised, asymmetric, flexible, dynamic
        
        selectively permeable
    - - lies outside plasma membrane
        
        peptidoglycan makes up cell wall (thicker in purple gram pos)
        
        peptidoglycan structure
        
        glucose molecules NAM and NAG
        
        1,4 glycosidic bond - lysozyme cleaves
        
        pentaglycine interbridge - crosslinking into 3D structure
        
        penicillin breaks pentaglycine bridge and stops transpeptidation
        
        teichoic acid
        
        anchors cell wall to plasma membrane
        
        only in gram pos
        
        lipopolysaccharides (LPS)
        
        only in gram neg
        
        plasma membrane < peptidoglycan < outer membrane < LPS
        
        consist of lipid A, core + polysaccharide, O antigen (lipid A toxin exposed when cell wall is broken ie. when heated)
        
        cell wall protection
        
        protects against osmotic lysis
        
        does not protect against plasmolysis (shrivelling)
    - - capsules
        
        composed of polysaccharides
        
        well organised, not easily removed from cell
      - slime layers
        
        help microbe move/propel
        
        diffuse, unorganised, easily removed
      - glycocalyx
        
        network of polysaccharides
        
        makes up capsule/slime layer
      - functions
        
        attachment to surfaces
        
        motility
        
        protection from environment (including hiding receptors from host defences)
  - - - similar to fimbriae except longer, thicker, less numerous
        
        required for mating - transfer of plasmids/genetic info
    - - short, thin
        
        attachment to surfaces
    - - motility
        
        structure:
        ~ filament [composed of flagellin protein]
        ~ basal body (anchors filament into cell) [series of rings that drive flagellar motor/turns flagella]
        ~ hook [links filament to basal body]
        
        chemotaxis
        
        movement towards chemical attractant or away from chemical repellant