Chapter 4 Functional Anatomy of Prokaryotic and Eukaryotic

Chapter 4 Functional Anatomy of Prokaryotic and Eukaryotic Cells

l Prokaryotes can be grouped based on morphology l l Genetically determined l Monomorphic vs pleomorphic Size Range l 0. 2 to 80 um in diameter l 2 to 600 um in length l Average size: 0. 2 -1. 0 µm × 2 - 8 µm

Morphology of Prokaryotic Cells l Prokaryotes exhibit a variety of shapes l Most common

l Spiral

l Uncommon Shapes Stella Haloarcula

l Cells may form groupings l Cells adhere together after division l Form characteristic arrangements l Depends on plan of division

Neisseria Enterococcus Micrococcus Sarcina Staphylococcus aureus

Bacillus anthracis Bacillus megaterium Bordetella pertussis

Layers External to Cell Wall l Glycocalyx l Made inside the cell; excreted to surface l General functions l Protection l Attachment l Motility

l Capsule or Slime Layer l Chemical composition varies depending on species

Flagella l l Naked filaments composed of flagellin Rotate clockwise/counterclockwise l Runs and tumbles l Taxis

l Flagella structure has three basic parts l Filament l Hook l Basal body

Polar - Monotrichous Polar -Lophotrichous Peritrichous Polar -amphitrichous

Axial filaments l Bundles of endoflagella that spiral around cell l Spirochete bacteria only l Corkscrew motion

Attachment Proteins l Fimbriae - bacteria l l l Hami – archaea l l l Filaments of pilin protein Attachment Hooked protein filament Attachment Sex Pili l l Pilin tubules Exchange of DNA

• • Cannulae – thermophilic archaea Spinae - marine bacteria • • Connect cells over distances Creates mesh-like network

Prokaryotic Cell Wall Determines shape of cell l Protects from osmotic pressure l Anchor point for flagella l Contributes to virulence l

l Unique chemical structure l Bacteria vs. Archaea l Gram positive vs. Gram-negative l Peptidoglycan (PTG) (murein) l Sugar found only in bacteria l Archaea may have proteins or alternate sugars

l Basic structure of PTG l Disaccharide polymer N-acetylglucosamin (NAG) l N-acetylmuramic acid (NAM) l l Glycan chain held together by amino acids l l Tetrapeptide chain Protein crossbridges may or may not be present l Mostly G+

l Gram positive cell wall l Thick layer of PTG l Teichoic acids Lipoteichoic or Wall teichoic acids l Polyalcohols that provide antigenic specificity l l May have external protein or sugar layer

l Gram-negative cell wall l Little or no PTG l Outer lipopolysaccharide membrane (LPS) O-specific polysaccharide side chain l Lipid A endotoxin l l Significant periplasmic space

GRAM STAINING l Gram-positive and gram-negative bacteria can be identified using a “gram stain”

Summary of Gram + vs. Gram – l G+ cell l l many rigid layers of peptidoglycan teichoic acids No outer LPS membrane 2 ring basal body anchoring flagella G- cell l l Little or no peptidoglycan no teichoic acids LPS outer membrane 4 ring basal body anchoring flagella

Atypical cell wall l Acid-fast cell walls l l Classified as gram-positive mycolic acid bound to PTG Mycobacterium Nocardia

l Chlamydia l l Classified as Gram – with no PTG cysteine-rich proteins

l No cell wall l Mycoplasmas l Sterols in plasma membrane

Structures Internal to Cell Wall l Cytoplasmic membrane l Delicate thin fluid structure l Defines boundary l Serves as a semi permeable barrier

l Fluid mosaic model l Phospholipid Bilayer l Amphipathic

l Embedded with numerous proteins l l receptors , transport, enzymes Prokaryotes typicallydon’t have membrane sterols l Bacteria may have hopanoids

l Photosynthetic pigments on in-foldings l chromatophores or thylakoids

l Archaea have distinct membrane lipids l Ether linkage l Diether l Glycerol or tetraether group enantiomer l Branched isoprenoid sidechain l May form mono-layer with greater rigidity

Top: archaeal phospholipid, 1 isoprene sidechain, 2 ether linkage, 3 L-glycerol, 4 phosphate group Middle: bacterial and eukaryotic phospholipid: 5 fatty acid, 6 ester linkage, 7 D-glycerol, 8 phosphate group Bottom: 9 lipid bilayer of bacteria and eukaryotes, 10 lipid monolayer of some archaea.

l Membrane is selectively permeable l Few molecules pass through freely l Movement involves both active and passive processes

l passive processes l no energy (ATP) required l Along gradient l simple diffusion, facilitated diffusion, osmosis

l Simple diffusion l Facilitated diffusion

l l Osmosis Osmotic pressure

l active processes l energy (ATP) required l Active transport

l Group translocation l Phosphotransferase system l PEP group translocation PEP transferase animation

Internal Structures essential for life l l l Chromosome Ribosome Optional but may provide selective advantage l l Cytoskeleton Plasmid Storage granules Endospores

Internal Structures l Primary Chromosome l l l Resides in nucleoid Typically single circular chromosome Archaea - histone proteins Bacteria - condensin protiens Asexual reproduction l Binary fission, budding, fragmenting, spores

l Plasmids l Small DNA molecules l replicated independently l nonessential information l used in genetic engineering biotechnology

l Ribosomes (70 S) l l Composed of large and small subunits l made of riboprotein and ribosomal RNA differ in density from eukaryotic ribosomes

• Inclusions l l l l Metachromatic granules Polysaccharide granules lipid inclusions sulfur granules carboxyzomes magnetosomes Gas vesicles

l Endospores l “Resting cells” l Highly resistant l Heat, desiccation, chemicals and UV light l Not reproduction! Endospore producers include Clostridium and Bacillus