Transcript E. coli
• Functional Anatomy of Prokaryotic and Eukaryotic Cells 2008 Prokaryotic Cells • Comparing Prokaryotic and Eukaryotic Cells • Prokaryote comes from the Greek words for prenucleus. • Eukaryote comes from the Greek words for true nucleus. 2008 Prokaryote Eukaryote • One circular chromosome, not in a membrane • Paired chromosomes, in nuclear membrane • No histones • Histones • No organelles • Organelles • Peptidoglycan cell walls • Polysaccharide cell walls • Binary fission • Mitotic spindle 2008 • Average size: 0.2 -1.0 µm 2 - 8 µm • Basic shapes: 2008 • Unusual shapes • Star-shaped Stella • Square Haloarcula • Most bacteria are monomorphic • A few are pleomorphic 2008 Figure 4.5 Arrangements • Pairs: diplococci, diplobacilli • Clusters: staphylococci • Chains: streptococci, streptobacilli 2008 Glycocalyx • Outside cell wall • Usually sticky • A capsule is neatly organized • A slime layer is unorganized & loose • Extracellular polysaccharide allows cell to attach • Capsules prevent phagocytosis 2008 Figure 4.6a, b Flagella • Outside cell wall • Made of chains of flagellin • Attached to a protein hook • Anchored to the wall and membrane by the basal body 2008 Figure 4.8 Flagella Arrangement 2008 Figure 4.7 Flagella arrangement flash animation 2008 2008 Figure 4.8 Flagella structure flash animation 2008 Motile Cells • Rotate flagella to run or tumble • Move toward or away from stimuli (taxis) • Flagella proteins are H antigens (e.g., E. coli O157:H7) 2008 Motile Cells 2008 Figure 4.9 Axial Filaments • Endoflagella • In spirochetes • Anchored at one end of a cell • Rotation causes cell to move 2008 Figure 4.10a Motility flash animation 2008 • Fimbriae allow attachment • Pili are used to transfer DNA from one cell to another 2008 Figure 4.11 Cell Wall • Prevents osmotic lysis • Made of peptidoglycan (in bacteria) 2008 Figure 4.6a, b Peptidoglycan • Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) • Linked by polypeptides 2008 Figure 4.13a 2008 Figure 4.13b, c Gram-positive cell walls Gram-negative cell walls • Thick peptidoglycan • Teichoic acids • In acid-fast cells, contains mycolic acid 2008 • Thin peptidoglycan • No teichoic acids • Outer membrane Gram-Positive cell walls • Teichoic acids: • Lipoteichoic acid links to plasma membrane • Wall teichoic acid links to peptidoglycan • May regulate movement of cations • Polysaccharides provide antigenic variation 2008 Figure 4.13b Gram-Negative Outer Membrane • Lipopolysaccharides, lipoproteins, phospholipids. • Forms the periplasm between the outer membrane and the plasma membrane. • Protection from phagocytes, complement, antibiotics. • O polysaccharide antigen, e.g., E. coli O157:H7. • Lipid A is an endotoxin. • Porins (proteins) form channels through membrane 2008 Gram-Negative Outer Membrane 2008 Figure 4.13c Gram Stain Mechanism • Crystal violet-iodine crystals form in cell • Gram-positive • Alcohol dehydrates peptidoglycan • CV-I crystals do not leave • Gram-negative • Alcohol dissolves outer membrane and leaves holes in peptidoglycan • CV-I washes out 2008 Atypical Cell Walls • Mycoplasmas • Lack cell walls • Sterols in plasma membrane • Archaea • Wall-less, or • Walls of pseudomurein (lack NAM and D amino acids) 2008 Damage to Cell Walls • Lysozyme digests disaccharide in peptidoglycan. • Penicillin inhibits peptide bridges in peptidoglycan. • Protoplast is a wall-less cell. • Spheroplast is a wall-less Gram-positive cell. • L forms are wall-less cells that swell into irregular shapes. • Protoplasts and spheroplasts are susceptible to osmotic lysis. 2008 Plasma Membrane 2008 Figure 4.14a Plasma Membrane • Phospholipid bilayer • Peripheral proteins • Integral proteins • Transmembrane proteins 2008 Figure 4.14b Fluid Mosaic Model • Membrane is as viscous as olive oil. • Proteins move to function • Phospholipids rotate and move laterally 2008 Figure 4.14b Plasma Membrane • Selective permeability allows passage of some molecules • Enzymes for ATP production • Photosynthetic pigments on foldings called chromatophores or thylakoids 2008 Plasma Membrane • Damage to the membrane by alcohols, quaternary ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents. 2008 Movement Across Membranes • Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration. • Facilitative diffusion: Solute combines with a transporter protein in the membrane. 2008 Movement Across Membranes 2008 Figure 4.17 Movement Across Membranes • Osmosis • Movement of water across a selectively permeable membrane from an area of high water concentration to an area of lower water. • Osmotic pressure • The pressure needed to stop the movement of water across the membrane. 2008 Figure 4.18a 2008 Figure 4.18c-e Movement Across Membranes • Active transport of substances requires a transporter protein and ATP. • Group translocation of substances requires a transporter protein and PEP. 2008 Cytoplasm • Cytoplasm is the substance inside the plasma membrane 2008 Figure 4.6a, b Nuclear Area • Nuclear area (nucleoid) 2008 Figure 4.6a, b Ribosomes Figure 4.6a 2008 Ribosomes Figure 4.19 2008 Inclusions • Metachromatic granules (volutin) •Phosphate reserves • Polysaccharide granules •Energy reserves • Lipid inclusions •Energy reserves • Sulfur granules •Energy reserves • Carboxysomes •Ribulose 1,5diphosphate carboxylase for CO2 fixation • Gas vacuoles •Protein covered cylinders • Magnetosomes •Iron oxide (destroys H2O2) 2008 Endospores • Resting cells • Resistant to desiccation, heat, chemicals • Bacillus, Clostridium • Sporulation: Endospore formation • Germination: Return to vegetative state 2008 2008 Figure 4.21a Eukaryotic Cells • Comparing Prokaryotic and Eukaryotic Cells • Prokaryote comes from the Greek words for prenucleus. • Eukaryote comes from the Greek words for true nucleus. 2008 2008 Figure 4.22a Flagella and Cilia 2008 Figure 4.23a, b • Microtubules • Tubulin • 9 pairs + 2 arrangements 2008 Figure 4.23c Cell Wall • Cell wall • Plants, algae, fungi • Carbohydrates • Cellulose, chitin, glucan, mannan • Glycocalyx • Carbohydrates extending from animal plasma membrane • Bonded to proteins and lipids in membrane 2008 Plasma Membrane • Phospholipid bilayer • Peripheral proteins • Integral proteins • Transmembrane proteins • Sterols • Glycocalyx carbohydrates 2008 Plasma Membrane • Selective permeability allows passage of some molecules • Simple diffusion • Facilitative diffusion • Osmosis • Active transport • Endocytosis • Phagocytosis: Pseudopods extend and engulf particles • Pinocytosis: Membrane folds inward bringing in fluid and dissolved substances 2008 Eukaryotic Cell • Cytoplasm membrane Substance inside plasma and outside nucleus • Cytosol Fluid portion of cytoplasm • Cytoskeleton Microfilaments, intermediate filaments, microtubules • Cytoplasmic streaming Movement of cytoplasm throughout cells 2008 Organelles • Membrane-bound: 2008 • Nucleus Contains chromosomes • ER Transport network • Golgi complex Membrane formation and secretion • Lysosome Digestive enzymes • Vacuole Brings food into cells and provides support • Mitochondrion Cellular respiration • Chloroplast Photosynthesis • Peroxisome Oxidation of fatty acids; destroys H2O2 Eukaryotic Cell • Not membrane-bound: • Ribosome Protein synthesis • Centrosome Consists of protein fibers and centrioles • Centriole Mitotic spindle formation 2008 Nucleus 2008 Figure 4.24 Endoplasmic Reticulum 2008 Figure 4.25 Ribosomes • 80S • Membrane-bound Attached to ER • Free In cytoplasm • 70S • In chloroplasts and mitochondria 2008 Golgi Complex 2008 Figure 4.26 Lysosomes 2008 Figure 4.22b Vacuoles 2008 Figure 4.22b Mitochondrion 2008 Figure 4.27 Chloroplast 2008 Figure 4.28 Endosymbiotic Theory 2008 Figure 10.2