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Cell Biomembrane

  1. Cell Biomembrane An Its Function
  2. CELL
  3. CELL WALL  Extremely porous  Peptidoglycan  Outer layer  Techoic acid  Outer membrane  It contribute to the ability of some species to cause diseases and is the site of action of some antibiotics
  4. COMPOSITION OF CELL WALL  Protein  Teichoic acid  Lipoteichoic acid  Peptidoglycan  Cell membrane  porin
  8. CHARACTERISTICS OF THE CELL WALLS OF GRAM POSITIVE AND NEGATIVE AND ACID FAST BACTERIA Characterisitics Gram positive Gram negative Acid fast Peptidoglycan Thick layer Thin layer Relatively small amount Teichoic acid Often present Absent Absent Lipids Very little present Lipopolysaccharides Mycolic acid and other waxes and glycolipids Outer membrane Absent Present Absent Periplasmic space Absent Present Absent Cell shape Always rigid Rigid or flexible Rigid or flexible Result of enzyme protoplast Sheroplast Difficult to digest Sensetivity to dyes and antibiotics Most sensetive Most sensetive Least sensetive Exapmles Staphylecoccus aureus Escherichia coli Mycobacterium tuberculosis
  9. PEPTIDOGLYCAN  A rigid polyssacharides.  It is composed of alternating reapets of two modified glucose residues called N- acetylglucosamine and N-acetylmuramic acid along with a amino acids L-lanine, D-alanine, D- glutamic acid, and either L-lysine or diaminopimolic acid (DAP) (NAG) (NAM).  Arranged in sheets individual sheets connected by peptide cross link.  Constituents are connected in an ordered way to from the glycan tetrapeptide.
  10. TEICHOIC ACIDS  Additional molecules of cell walls of gram positive organisms.  compositions:- glycerol sugar alcohol (ribitol) phosphate length = upto 30  It is covalently bonded to membrane lipids rather that to peptidoglucan, and these are called lipoteictoic acids.  Extended beyond the rest of the cell wall, even beyond the capsule in encapsulated bacteria.
  11. FUNCTIONS OF TEICHOIC ACIDS  Furnished attachment sites for bacteriophage.  Probably serves as a passage way for movement of icons into and out of the cell.
  12. OUTER MEMBRANE  Found primarily in the gram negative bacteria only a small amount of the toal cell consist of peptidoglycan as most of thecell wall is composed of the outer membrane.  It is bilayer membrane.  It is attached to the peptidoglycan by an almost continous layer of small lipoprotein molecules.  These large, complex molecules contain both lipid and carbohydrates.
  13. LIPID A  Two glucosamine sugar derivatives  Fatty acids A  phosphate
  14.  Core polysaccharide :- - 10 sugar  O side chain oro antigen :- - polysaccharides chain extending
  15. FUNCTION  It contribute to the negative charge on the bacterial surface because the core polysaccharides usually contains charged sugar and phosphate.  It hepls create a permeability barries.