Ch4-cell structure - Prokaryotic Cells • Comparing...

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Unformatted text preview: Prokaryotic Cells • Comparing Prokaryotic and Eukaryotic Cells • Prokaryote comes from the Greek words for prenucleus. • Eukaryote comes from the Greek words for true nucleus. Differentiation of Prokaryotes • Morphology • Chemical composition • Nutritional requirements • Biochemical activities • Source of energy • One circular chromosome, not in a membrane • No histones • No organelles • Peptidoglycan cell walls • Binary fission Prokaryote Eukaryote • Paired chromosomes, in nuclear membrane • Histones • Organelles • Polysaccharide cell walls • Mitotic spindle • Average size: 0.2 -1.0 µm × 2 - 8 µm • Basic shapes: • Unusual shapes • Star-shaped Stella • Square Haloarcula • Most bacteria are monomorphic • A few are pleomorphic Figure 4.5 • Pairs: diplococci, diplobacilli • Clusters: staphylococci • Chains: streptococci, streptobacilli Arrangements • Outside cell wall • Usually sticky • A capsule is neatly organized • A slime layer is unorganized & loose • Extracellular polysaccharide allows cell to attach • Capsules prevent phagocytosis Glycocalyx Figure 4.6a, b • Outside cell wall • Made of chains of flagellin • Attached to a protein hook • Anchored to the wall and membrane by the basal body Flagella Figure 4.8 Flagella Arrangement Figure 4.7 Figure 4.8 • Rotate flagella to run or tumble • Move toward or away from stimuli (taxis) • Flagella proteins are H antigens (e.g., E. coli O157:H7) Motile Cells Motile Cells Figure 4.9 • Endoflagella • In spirochetes • Anchored at one end of a cell • Rotation causes cell to move Axial Filaments Figure 4.10a • Fimbriae allow attachment • Pili are used to transfer DNA from one cell to another Figure 4.11 Conjugation • http://www.microbelibrary.org/microbelibrary/files/ccImage • Prevents osmotic lysis • Made of peptidoglycan (in bacteria) Cell Wall Figure 4.6a, b • Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) • Linked by polypeptides Peptidoglycan Figure 4.13a Gram + Cell Wall Gram - Cell Wall •...
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Ch4-cell structure - Prokaryotic Cells • Comparing...

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