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Unformatted text preview: PowerLecture: PowerLecture: Chapter 21
Prokaryotes the simple cells and Noncells: Viruses, Prions and Viroids Microorganisms Microorganisms Singlecelled organisms that are too small to be seen without a microscope Bacteria are the smallest living organisms Viruses, Prions and Viroids are smaller but are not alive The Prokaryotes The Prokaryotes Only two groups Archaebacteria and Eubacteria Arose before the eukaryotes CHARACTERISTICS No membranebound nucleus Unicellular Single chromosome Cell wall (in most species) Prokaryotic fission Metabolic diversity Prokaryotic Body Plan
cytoplasm, with ribosomes DNA, in nucleoid pilus bacterial flagellum outer capsule cell wall plasma membrane Fig. 21-2, p.334 Bacterial Shapes:MOST OF THE EUBACTERIA ARE Bacterial Shapes
ONE OF THE FOLLOWING SHAPES, BUT ARE SO SMALL THAT TO TELL THEM APART USUALLY BIOCHEMICAL MEANS, OR ANALYSIS OF THEIR METABOLISM ARE USED coccus bacillus spirillum p. 334 Gram Stain Fig. 21-4, p.335 Eubacterial Metabolic Diversity Eubacterial Metabolic Diversity Photoautotrophic:Use light for energy inorganic compounds for carbon source Chemoautotrophic:Use inorganic compounds for energy and carbon source Aerobic (Cyanobacteria) Anaerobic (Green bacteria) ChemoheterotrophicUse organic compounds for energy and carbon source Important in nitrogen cycle Largest group Bacterial Genes Bacterial Genes Bacteria have a single chromosome Circular molecule of DNA Selfreplicating circle of DNA that has a few genes Can be passed from one cell to another Many bacteria also have plasmids Prokaryotic Fission Fig. 21-5, p.335 Bacterial Behavior Bacterial Behavior Bacteria move toward nutrientrich regions Aerobes move toward oxygen; anaerobes avoid it Photosynthetic types move toward light Magnetotactic bacteria swim downward Myxobacteria show collective behavior Some Bacteria are harmful Some Bacteria are harmful Some Eubacteria arePathogenic and can cause diseases such as:Botulism, Staph infections, Pathogenic E.coli, Strep throat and TB They may also cause diseases in other animals and plants Some are Beneficial Some are Beneficial Some fix Nitrogen in the nitrogen cycle Some are used in genetic engineering Some live naturally on our bodies and protect us from pathogens Some even help us produce our Vitamin K ARCHAEA:THE NEW DOMAIN OF ARCHAEA:
PROKARYOTES THEY DIFFER FROM THE EUBACTERIA IN THE COMPOSITION OF THEIR CELL WALL, THEIR CELL MEMBRANE AND IN MANY THEIR ABILITY TO LIVE IN EXTREME ENVIRONMENTS. The METHANOGENS live in cow stomachs and produce methane The THERMOPHILES can live in hydrothermal vents in temperatures over the boiling point The HALOPHILES can live in salt flats, which kills most other organisms Virus Virus Noncellular infectious agent Protein wrapped around a nucleic acid core Cannot reproduce itself; can only be reproduced using a host cell Are considered to be NONLIVING because they are not composed of cells. Viral Body Plans Viral Body Plans Complex virus (bacteriophage) Genetic material is DNA or RNA Coat is protein Helical virus Polyhedral virus
Fig. 21-13, p.342 Viral Multiplication Basic Steps Viral Multiplication Basic Steps Attach to host cell Enter host (virus or just genetic material) Direct host to make viral genetic material and protein Assemble viral nucleic acids and proteins Release new viral particles Lytic Lytic Pathway Lysis of host cell is induced; infectious particles escape. Tail fibers and other parts are added to coats. Virus particles bind to wall of suitable host. Viral genetic material enters cell cytoplasm. Viral protein molecules are assembled into coats; DNA is packaged inside. Viral DNA directs host machinery to produce viral proteins and viral DNA. Stepped Art Fig. 21.20 Page 358 Lysogenic Lysogenic Pathway
Viral DNA usually becomes integrated into the bacterial chromosome. Viral DNA is excised from chromosome and cell enters lytic pathway. Prior to prokaryotic fission, the chromosome and integrated viral DNA are replicated. After binary fission, each daughter cell will have recombinant DNA. Stepped Art Fig 21.20 (2) Page 358 OTHER NON LIVING INFECTIOUS AGENTS OTHER NON LIVING INFECTIOUS AGENTS
VIROIDS Smaller than viruses Strands or circles of RNA No proteincoding genes No protein coat Cause many plant diseases PRIONS Small proteins Linked to human diseases Kuru CreutzfeldtJakob disease (CJD) Animal diseases Scrapie in sheep Bovine spongiform encephalopathy (mad cow disease) Evolution and Disease Evolution and Disease Host and pathogen are coevolving If a pathogen kills too quickly, it might disappear along with the individual host Most dangerous if pathogen Is overwhelming in numbers Is in a novel host Is a mutant strain SMALL BUT IMPORTANT SMALL BUT IMPORTANT
NATURE OF DISEASE Contagious disease pathogens must directly contact a new host Epidemic :spreads within a population, then subsides Pandemic (AIDS):breaks out in many areas of the world at the same time Sporadic Endemic NEW THREATS see pages 343,346 Emerging Pathogens Ebola virus Monkeypox virus SARS virus Drugresistant strains Food poisoning E. coli Salmonella . ...
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