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Anatomy of Procaryotic Cells

Anatomy of Procaryotic Cells. Cell Wall. Wall structure based on peptidoglycan polysaccharide composed of 2 sugars N-acetylglucoseamine NAG N-acetylmuramic acid polypeptide short amino acid chains that link the polysaccharides together. Gram + cell wall. Many layers of peptidoglycan

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Anatomy of Procaryotic Cells

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  1. Anatomy of Procaryotic Cells

  2. Cell Wall • Wall structure based on peptidoglycan • polysaccharide composed of 2 sugars • N-acetylglucoseamine NAG • N-acetylmuramic acid • polypeptide short amino acid chains that link the polysaccharides together

  3. Gram + cell wall • Many layers of peptidoglycan • has teichoic acids which connect layers of PG together and connect wall to plasma membrane • antigenic & recognition site • allows for expansion of wall • controls movement of + ion in/out of cell • streptococci & Mycobacterium are variation

  4. Gram - cell wall • One layer of peptidoglycan in periplasmic space (jelly-like in nature) • PG covered by outer membrane composed of phospholipid, along with lipoprotein, and lipopolysaccharide • lipoprotein - connects wall to plasma membrane • lipopolysacharide includes O antigens and • lipid A (an endotoxin)

  5. Functions of outer membrane • negative charge helps avoid phagocytosis • barrier to entry • porins allow nutrients to enter

  6. Atypical Cell Walls • Mycoplasma - smallest bacteria known; little of no wall; plasma membrane has sterols to help prevent bursting • Archaea - have cells walls similar to PG but not the same (one sugar is different)

  7. Cell wall damage • Lysozyme (enzyme) cuts NAG-NAM linkages • Penicillin prevents peptide bridge formation; doesn’t break bridges but prevents forming new ones when cell is growing and adding more wall • most effective when bacteria are growing and adding new wall

  8. Protoplast - entire gram + wall removed (such as treatment w lysozyme); subject to lysis; spherical • Spheroplast - gram - wall is weakened; wall present but weak; spherical

  9. Plasma (cell) membrane • Composed of phospholipid and protein • phospholipid bilayer - nonpolar tails (not water soluble) face inside; polar “heads” facing surface (water soluble) • proteins are suspended in phospholipid • peripheral proteins on surface; easily removed • integral proteins - some go all the way through the bilayer

  10. “fluid mosaic model” protein icebergs in a sea of phospholipid • plasma membrane is self-sealing • functions: • encloses • selective barrier (selectively permeable) • because of molecule size, solubility in lipid, carrier molecules

  11. Site of chemical reactions (particularly respiration, photosynthesis) • to destroy membranes • use alcohol, ammonium compounds, some antibiotics will dissolve phospholipid • also damages human cells (must be used carefully or used as disinfectant)

  12. Regulation of movement across membranes • Some methods are passive (require no energy from cell - energy comes from molecules that are moving) • simple diffusion, facilitated diffusion, osmosis • active methods - uses cell’s energy (ATP) • active transport, group translocation

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