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BMS1021: cells, tissues and organisms: Lecture 2,3 and 4 summaries

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Monash University
Biomedical Sciences
John Bertram

Lecture Summaries Lecture 2 Summary: Each species has two-part name: first part is genus and second part is species. - E.g. Escherichia coli – genus = Escherichia, species = coli. •Six kingdoms and two domains: Eukaryotic: - Animalia : multicellular animals - Planta : multicellular plants - Fungi: multicellular fungi and unicellular yeasts - Protista: unicellular algae and protozoa Prokaryotic: - Archaea (or Archaebacteria): diverse group of organisms that often live under extreme environmental conditions E.g. high salt/temperature. - Bacteria Differences between prokaryotic cells and eukaryotic cells: Structure of nucleus: prokaryotic nuclear material not surrounded by membrane  eukaryotes: - several chromosomes - diploid - mitosis/ meiosis - Membrane bound organelles  prokaryotes: - single circular chromosome - haploid - binary fission - no membrane bound organelles Selective toxicity: • Choose an antimicrobial agent whose mechanism of action targets a biochemical process that only occurs in bacteria • Inhibit that process – kill prokaryotic cell – no effect on mammalian cell because it does not carry out that process E.g. Penicillin : - peptidoglycan is an essential structural component of bacterial cell wall – not found in human cells – good target for selective toxicity – penicillins inhibit synthesis of peptidoglycan Bacteria: - bacteria vary in size : 0.1micrometers to 50micrometers in diameter Gram Staining: Gram positive (+) cell wall: - Thick peptidoglycan layer - No outer membrane - Crystal violet iodine complex trapped inside cell - Purple - Rods or cocci - may form heat resistant endospores Gram Negative (-) cell wall: - Thin peptidoglycan layer - Lipopolysaccharides in cell wall - Rods or cocci Basis for gram stain technique: differences in thickness of peptidoglycan layer Lecture 3 Summary: Bacteria have external structures like: flagella, Pili or fimbriae, and capsules. Flagella: - can be peritrichous or polar - motility - not all bacteria have flagella and therefore some are not motile - they move in unison Fimbriae/pili - shorter than flagella and more numerous -not involved in motility, and not in all bacteria - important in pathogenesis - Primary role is adhesion - to allow bacteria to adhere to mammalian cells Capsules: Many bacteria secrete a slimy layer onto their cell surface - usually a polysaccharide complex - important in pathogenesis - prevention of phagocytosis by host cells Bacterial cell division: Through Binary Fission: Sporulation: - Some bacteria produce heat resistant endospores - Resistant to environmental stress All microorganisms (all organisms) have three fundamental requirements that are essential for their growth: • Energy • Carbon • Nitrogen – All have need for P, Mg, Ca and trace elements Bacteria reproduce asexually but there are me
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