Chap 27 Prokaryotes-st

Chap 27 Prokaryotes-st - Prokaryotes-Chap 27 The three...

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The three major clades, often referred to as the three domains: Archaea, Bacteria, and Eukaryota. -largest biomass Prokaryotes- Do not have membrane, cytoskeletal elements, specialized organelles, unicellular -great diversity bc short generation span allows them to accumulate mutations Protozoa -eukaryote, membranous organelles, unicellular Prokaryotes-Chap 27
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Prokaryotes Bacteria were first discovered in the late 1600’s by Antony van Leeuwenhoek, using the microscope he invented. The first recorded observation were of the bacteria found in the dental plaque of two old men who never cleaned their teeth. Biofilms- bacteria form biofilms using quorum sensing to sense the population around them and bring more
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Prokaryote Introduction Prokaryotes are much more diverse in both habitat and metabolism than the eukaryotes. Bacterial interactions- parasitism, mutualism In cows bacteria digests cellulose and gives methane Bacteria in intestines attracts blood vessels, improves food absorption
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Prokaryote Structure The cell is surrounded by a membrane,. a cell wall, sometimes an outer capsule Flagella- taxis [response to certain stimuli] Pilli used to attach Fimbriae- useful for infecting hosts, sticky Mycoplasma- no cell wall, smallest, bursts in hypotonic Monotrichous-one on one side Lopotrichous-many on one side Amphitrichous-one on each side Peritrichous- all over
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Gram + and Gram - bacteria Using a technique called the Gram stain Scientists can classify many bacterial species into two groups based on cell wall composition, Gram-positive and Gram-negative (a) Gram-positive. Gram-positive bacteria have a cell wall with a large amount of peptidoglycan that traps the violet dye in the cytoplasm. The alcohol rinse does not remove the violet dye, which masks the added red dye. (b) Gram-negative. Gram-negative bacteria have less peptidoglycan , and it is located in a layer between the plasma membrane and an outer membrane. The violet dye is easily rinsed from the cytoplasm, and the cell appears pink or red after the red dye is added. Figure 27.3a, b Peptidoglycan layer Cell wall Plasma membrane Protein Gram- positive bacteria 20 μ m Outer membrane Peptidoglycan layer Plasma membrane Cell wall Lipopolysaccharide Protein Gram- negative bacteria -Lipopolysaccharides in G- determine toxicity [less affected by antibiotics, penicillin] Usually have fimbriae
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Bacterial Morphology Prokaryotic cells have a variety of shapes The three most common of which are spheres
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Chap 27 Prokaryotes-st - Prokaryotes-Chap 27 The three...

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