Transcript Chapter 4
Chapter 4 Functional Anatomy of Prokaryotic and Eukaryotic Cells Definition of “prokaryotic” Refers to organisms, typically 1-celled, having cells which: – lack a nucleus – lack membrane-bound organelles – contain 1 chromosome – may contain extra-chromomal DNA (plasmids) – contain 70S ribosomes – contain peptidoglycan cell walls Prokaryotic vs. Eukaryotic cells Kingdom Monera divided into three major groups or Subkingdoms Kingdom Monera Eubacteria Archaebacteria Cyanobacteria Bacterial cell size, shapes and arrangements • 2.0 – 10.0 uM in length • Eukaryotic cells ~10x larger • 3 common morphologies – bacillus = rod-shaped – coccus = spherical shaped – spirillum = spiral shaped • Many arrangements – diplo– strepto– Staphylo***spirochetes** Bacterial morphologies • Morphology can be used as an initial identifier • However, shape can change in some bacteria depending on environs – “pleomorphic” cells Bacterial ultrastructure 1) Cell wall structure • Alternating NAM & NAG amine sugars produce layers of block units – NAM = n-acetylmuramic acid – NAG = n-acetylglucosamine Make up peptidoglycan • Layers connected by tetrapeptide chains linked to NAM’s • Penta-glycine interbridges connect tetrapeptides in Gram + cells (sensitive to penicillin) • Direct peptide bonds connect tetrapeptides in Gram – cells (not sensitive to penicillin) Alternating NAM-NAG with tetrapeptide connections Gram positive cell wall structure Ok, not too bad – now for something completely different – Gram negative cell walls! Gram negative cell wall structure Gram neg. cell walls are composed of peptidoglycan AND an outer membrane; it is multi-layered!! Gram negative LPS* • *Lipopolysaccharide contains 3 parts: – Antigen O – can change shape in dif’t environs – Core polysaccharide – contains neg. charge – Lipid A – also called ‘endotoxin A’; released upon cell death and can have toxic affect on nearby cell membranes Gram pos. vs Gram neg cell walls Gram + • Thick peptidoglycan – 20-80 nm thick • Retains CV-I complex of Gram stain • Teichoic acid anchors cell wall to cell membrane and imparts a negative charge – Glycerol-P polymer Gram - • Two part structure – Thin peptidoglycan (10-20 nm) – Outer membrane • Outer membrane contains LPS • LPS imparts a negative charge The Gram stain 2) Bacterial flagella • Composed of: 1) basal body, 2) filament, 3) hook • Basal body connects to cell wall and to cell membrane • Uses ATP to spin Arrangements of flagella Bacteria are hampered to some extent by flagellar rotation