Prokaryotic Cells Morphology Specialized Structures Ultrastructure Prokaryotic Cell
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Prokaryotic Cells Morphology Specialized Structures Ultrastructure
Prokaryotic Cell l Size, Shape & Arrangement – 0. 2 µm to 2. 0 µm diameter – 2 µm to 8 µm in length – Three basic shapes » cocci (spheres) » bacillus (rods) » spirochete (twisted/spiral) – Pleomorphic shapes
Prokaryotic Cells l Characteristics – Smaller than eukaryotic cells – No nuclei or chromosomes – No membrane-bound internal organelles – Circular genomic DNA – 70 S Ribosomes – Cell division by binary fission – No meiosis; recombination by transfer of DNA fragments
Prokaryotic Cell l Cocci – spheres – Staphylo- clusters – Strepto- chains
Prokaryotic Cell l Bacilli – rods
Prokaryotic Cell l Spirochete – spirals
Prokaryotic Cells l Specialized Structures – Endospores – a structure produce primarily by Clostridia and Bacillus species to resist desication – Acid Fast Bacteria – a waxy sheet or coat produced by Mycobacteria – Club shape – produced by Corneybacteria
Prokaryotic Cells l l l Flagella Capsules Cell envelope l l Fimbriae Pili
Prokaryotic Cells
Prokaryotic Cells l Flagella – Long filamentous protein » filament » hook » basal body – Rotates to propel cell – Taxis (positive and negative)
Prokaryotic Cells l Capsules – Slime layer – Polysaccharide or polypeptide – Protection from phagocytosis by host – “Stickiness” permits adherence – Prevents desication
Prokaryotic Cells l Cell Envelope or Cell Wall – Gram positive » Peptidoglycan (Multi layer) » Teichoic acid – Gram negative » Peptidoglycan (single layer) » Outer membrane (lipopolysaccharide) – Primary function is resist changes in osmotic pressure; also functions in recognition
Prokaryotic Cells l Peptidoglycan – N-acetylglucosamine – N-acetylmuramic acid – Peptide composed of D - and L- amino acids
Prokaryotic Cells
Prokaryotic Cells l Lipopolysaccharide – Outer membrane of Gram negative cells – Composed of lipid and carbohydrate – Carbohydrate referred to as O-antigen – Associated with some endotoxins in pathogenic G- bacteria
Prokaryotic Cells
Prokaryotic Cells l Teichoic Acid – sugar alcohol plus phosphate
Prokaryotic Cells l Fimbriae – associated with the adhesiveness of cells to surfaces
Prokaryotic Cells l Pili – involved in the transfer of genetic material
Prokaryotic Cells l Internal Structures – Generally no internal structures – Some bacteria produce polyalkonate granules when carbon is in surplus and nitrogen is limiting