Transcript Rotavirus
Eukaryote • Nucleus • Paired chromosomes • Organelles • Polysaccharide cell walls • Mitotic spindle Prokaryote No Nucleus One circular chromosome No organelles Peptidoglycan cell walls Binary fission Average size: 0.2 -1.0 µm 2 - 8 µm Are unicellular and most multiply by binary fission Basic shapes: COCCUS BACILLUS SPIRAL Arrangements Pairs: Diplococci, Diplobacilli Clusters: Staphylococci Chains: Streptococci, Streptobacilli Arrangements of cocci: Determined by division of planes. Arrangements of bacilli: Determined by division of planes. Arrangements of Spiral bacteria Double-stranded helix formed by Bacillus subtilis. Bacterial structure Prokaryote cell Glycocalyx Outside cell wall Usually sticky Capsule: Prevent phagocytosis A slime layer is unorganized & loose glycocalyx Extracellular polysaccharide (EPS) allows cell to attach Figure 4.6a, b Flagella Long filamentous appendages Outside cell wall Made of chains of flagellin Attached to a protein hook Anchored to the wall and membrane by the basal body Flagella Arrangement Four arrangements of flagella: Fimbriae and Pili Short, thin appendages Attachment Cell Wall Prevents osmotic lysis Made of peptidoglycan Contributes to disease capability and site of action of some antibiotics. Peptidoglycan Polymer of disaccharide: N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) Linked by polypeptides Small arrows: Where penicillin interferes with linkage of peptidoglycan rows Gram positive vs. gram negative cell walls Gram-positive cell walls Thick peptidoglycan Teichoic acids (alcohol+phosphate) In acid-fast cells, contains mycolic acid (waxy lipid): Allows them to be grouped into medically significant types. Gram-negative cell walls • • Thin peptidoglycan • Outer membrane: No teichoic acids o o Prevent phagocytosis Barrier to certain antibiotics Gram-Positive cell walls Teichoic acids: – Lipoteichoic acid links to plasma membrane – Wall teichoic acid links to peptidoglycan May regulate movement of cations (+ charge) Polysaccharides provide antigenic variation (Identification) Gram-Negative Outer Membrane Lipopolysaccharides, lipoproteins, phospholipids. Forms the periplasm between the outer membrane and the plasma membrane. Protection from phagocytes, antibiotics, and complement (30+ liver proteins that protect host). O polysaccharide antigen, e.g., E. coli O157:H7. Lipid A is an endotoxin. Porins (proteins) form channels through membrane to pass other molecules Gram-Negative Outer Membrane Damage to Cell Walls Lysozyme digests disaccharide in peptidoglycan (Gram+ve cell walls: Destroyed, Gram-ve cell wall: Damaged). Penicillin inhibits peptide bridges in peptidoglycan. Plasma Membrane Plasma Membrane: Fluid Mosaic Model Selectively permeable Phospholipid bilayer Peripheral proteins Integral proteins Transmembrane proteins Figure 4.14b Fluid Mosaic Model Membrane is as viscous as olive oil. Proteins: Movable Phospholipids: Movable Plasma Membrane Carry enzymes for metabolic reactions: nutrient breakdown, energy production, photosynthesis Selective permeability allows passage of some molecules Enzymes for ATP production Photosynthetic pigments on foldings called thylakoids Damage to the membrane by detergents, and polymyxin antibiotics causes leakage of cell contents.