Contains n acetyl glucosamine and n acetylmuramic

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contains N-acetyl glucosamine and N- acetylmuramic acid and several different amino acids chains of linked peptidoglycan subunits are cross linked by peptides 35
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Gram-Positive Cell Walls Composed primarily of peptidoglycan Contain large amounts of teichoic acids (- charged) attached either to the peptidoglycan layer or the plasma membrane Presents a small periplasmic space with relatively few proteins Periplasm : lies between plasma membrane and cell wall and is smaller than that of Gram - bacteria Enzymes secreted by Gram + bacteria are called exoenzymes 36
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Gram-Positive Cell Walls 37
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Gram-Negative Cell Walls Consist of a thin layer of peptidoglycan surrounded by an outer membrane Outer membrane composed of lipids, lipoproteins, and lipopolysaccharide (LPS) NO teichoic acids More complex than gram + walls Peptidoglycan is ~2-5% of wall weight Periplasmic space differs from that in gram + cells may constitute 20-40% of cell volume many enzymes present in periplasm 38
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Gram-Negative Cell Walls 39
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protection from host defenses (O antigen) contributes to negative charge on cell surface (core polysaccharide) helps stabilize outer membrane structure (lipid A) can act as an exotoxin (lipid A) Lipopolysaccharides (LPSs) consists of three parts lipid A core polysaccharide O side chain (O antigen) 40
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The Cell Wall and Osmotic Protection osmotic lysis can occur when cells are in hypotonic solutions movement of water into cell causes swelling and lysis due to osmotic pressure cell wall protects against osmotic lysis Lysozyme breaks the bond between N-acetyl glucosamine and N- acetylmuramic acid Penicillin inhibits peptidoglycan synthesis If cells are treated with either of the above they will lyse if they are in a hypotonic solution 42
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Glycocalyx layers Polysaccharide based external to the cell wall - 1) capsules (Antrax) Usually composed of polysaccharides Loosely attached permits escape from phagocytosis - 2) slime layers (cavities) Thinner than a capsule, is tightly bound to the cell wall and adhered to surfaces (biofilm) Offer protection against dehydration 43
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Internal Structures Cytoplasm: the semifluid substance inside the cell Ribosomes: protein-RNA structures necessary for protein synthesis, scattered within the cytosol Nuclear Region: region of the cytosol where the genome of the cell aggregates Inclusion/granules,vessicles: a variety of small bodies with accumulation of cellular material Endospores: produced in vegetative cells as means of survival in adverse conditions. Not all bacteria produce them ( Bacillus and Clostridium )
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Appendages Appendages either anchor bacteria to a surface or aid in the process of locomotion.
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