Presentation on theme: "Functional Anatomy of Prokaryotic and Eukaryotic Cells"— Presentation transcript:
1Functional Anatomy of Prokaryotic and Eukaryotic Cells Chapter 4Functional Anatomy of Prokaryotic and Eukaryotic Cells
2Prokaryotic Cells Comparing Prokaryotic and Eukaryotic Cells Learning objective: compare and contrast overall cell structure of prokaryotes and eukaryotes.Comparing Prokaryotic and Eukaryotic CellsProkaryote comes from the Greek words for prenucleus.Eukaryote comes from the Greek words for true nucleus.
3Prokaryote Eukaryote Cell membrane Cytoplasm One circular chromosome, not in a membraneNo histonesNo organellesPeptidoglycan cell wallsBinary fissionCell membraneCytoplasmPaired chromosomes, in nuclear membraneHistonesOrganellesPolysaccharide cell wallsMitotic spindle
4Average size: 0.2 -1.0 µm 2 - 8 µm (1 x 10-6 m) Learning objective: Identify the three basic shapes of bacteria.Average size: µm µm (1 x 10-6 m)Are unicellular and most multiply by binary fissionBasic shapes:COCCUS BACILLUS SPIRAL
9Double-stranded helix formed by Bacillus subtilis. Bacillus cells often remain attached to each other, forming extended chains.
10Unusual shapes (Prokaryotes) Star-shaped Stella Square Haloarcula (halophilic archaea – salt-loving)Most bacteria are monomorphic (single shape)A few are pleomorphic (many shapes)Figure 4.5
11Learning objective: Describe the structure and function of the glycocalyx, flagella, axial filaments, fimbriae, and pili.Prokaryote cell
12Glycocalyx Outside cell wall Usually sticky A capsule is neatly organizedA slime layer is unorganized & loose glycocalyxExtracellular polysaccharide (EPS) allows cell to attachCapsules prevent phagocytosisProtects against dehydration or loss of nutrients.Figure 4.6a, b
13FlagellaLong filamentous appendages of a filament, hook, and basal bodyOutside cell wallMade of chains of flagellinAttached to a protein hookAnchored to the wall and membrane by the basal bodyFigure 4.8
14Flagella ArrangementFour arrangements of flagella:Figure 4.7
15Motile Cells Rotate flagella to run or tumble Move toward or away from stimuli (positive and negative taxis)Flagella H proteins are antigens (e.g., E. coli O157:H7)
16Motile CellsA Proteus cell swarming may have peritrichous flagella. (from all sides)Figure 4.9
17Axial Filaments (endoflagellum) EndoflagellaIn spirochetesAnchored at one end of a cellRotation causes cell to moveFigure 4.10a
18Fimbriae and Pili Are short, thin appendages Fimbriae of this E. Coli cell allow attachment (velcro). Cell is beginning to divide.Pili are used to transfer DNA from one cell to anotherFigure 4.11
19Learning objectives: Compare/contrast cell walls of gram-positive bacteria, gram-negative bacteria, archaea, and mycoplasmas.Differentiate between protoplast, spheroplast, and L form.Cell WallPrevents osmotic lysis (protects against changes in water pressure)Made of peptidoglycan (in bacteria = NAG+NAM+amino acids) – penicillin interferes with production of peptidoglycanContributes to disease capability and site of action of some antibiotics.Figure 4.6a, b
20Peptidoglycan (murein) Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)Linked by polypeptidesThe small arrows denote where penicillin interferes with linkage of peptidoglycan rows.Figure 4.13a
21Gram positive vs. gram negative cell walls Figure 4.13b, c
22Gram-positive cell walls Gram-negative cell walls Thick peptidoglycanTeichoic acids (alcohol+phosphate)In acid-fast cells, contains mycolic acid (waxy lipid) – allows them to be grouped into medically significant types.Thin peptidoglycan (subject to mechanical breakage)No teichoic acidsOuter membrane:Evades phagocytosisBarrier to certain anti-biotics
23Gram-Positive cell walls Teichoic acids:Lipoteichoic acid links to plasma membraneWall teichoic acid links to peptidoglycanMay regulate movement of cations (+ charge)Polysaccharides provide antigenic variation (identification)Figure 4.13b
24Gram-Negative Outer Membrane Lipopolysaccharides, lipoproteins, phospholipids.Forms the periplasm between the outer membrane and the plasma membrane.Protection from phagocytes, complement (30+ liver proteins that protect host), antibiotics.O polysaccharide antigen, e.g., E. coli O157:H7.Lipid A is an endotoxin.Porins (proteins) form channels through membrane to pass other molecules
26Gram Stain MechanismCrystal violet-iodine (CV-I) crystals form in cell combining with peptidoglycanGram-positiveAlcohol dehydrates peptidoglycanCV-I crystals do not leaveGram-negativeAlcohol dissolves outer membrane and leaves holes in peptidoglycanCV-I washes out
29Atypical Cell Walls Mycoplasmas (Genus) Lack cell walls Sterols in plasma membraneArchaeaWall-less, orWalls of pseudomurein (lack NAM and D amino acids, peptidoglycan)
30Damage to Cell WallsLysozyme digests disaccharide in peptidoglycan (gram+ cell walls destroyed, gram- damaged, resulting in spheroplast).Spheroplast is a wall-less Gram-positive cell.Penicillin inhibits peptide bridges in peptidoglycan.Protoplast is a wall-less cell.L forms are wall-less cells that swell into irregular shapes (gram+ and -).Protoplasts and spheroplasts are susceptible to osmotic lysis.
31Plasma (cytoplasmic) Membrane Learning objectives: Describe the structure, chemistry, and functions of prokaryotic plasma membrane.Define simple diffusion, facilitated diffusion, osmosis, active transport, and group translocation.Figure 4.14a
34Fluid Mosaic Model Membrane is as viscous as olive oil. Proteins move to functionPhospholipids rotate and move laterallyFigure 4.14b
35Plasma MembraneCarry enzymes for metabolic reactions: nutrient breakdown, energy production, photosynthesisSelective permeability allows passage of some moleculesEnzymes for ATP productionPhotosynthetic pigments on foldings called chromatophores or thylakoidsDamage to the membrane by alcohols, quaternary ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents.
37Movement Across Membranes High to low concentration:Movement may be passive (no energy expenditure – diffusion or facilitated diffusion):Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration. (ions move until equilibrium reached)Facilitative diffusion: Solute combines with a transporter protein in the membrane.
39Movement Across Membranes Osmosis (always involves water):Movement of water across a selectively permeable membrane from an area of high water concentration to an area of lower water.Osmotic pressureThe pressure needed to stop the movement of water across the membrane.Figure 4.18a
41Movement Across Membranes Low to high concentration (against gradient) – cell must expend energy:Active transport of substances requires a transporter protein and ATP.Group translocation of substances requires a transporter protein and PEP. (phospheonolpyruvic acid)
42CytoplasmCytoplasm is the fluid substance inside the plasma membrane (water, inorganic and organic molecules, DNA, ribosomes, and inclusions)Figure 4.6a, b
44Nuclear AreaLearning objectives: Identify functions of the nuclear area, ribosomes, and inclusions.Nuclear area (nucleoid) – contains single long, continuous, double-stranded DNA called bacterial chromosome.Bacteria can contain plasmids – circular DNAFigure 4.6a, b
45Ribosomes = rRNA + proteins Sites of protein synthesis (rRNA) – free floating, not tied to endoplasmic reticulum as in eukaryotes.Figure 4.6a
46RibosomesThe letter S refers to Svedberg units = relative rate of sedimentation.Because of differences in prokaryotic and eukaryotic ribosomes, the microbe can be killed by antibiotics while eukaryotic host cell is unaffected.Figure 4.19
48Iron-oxide inclusions in some gram-negative bacteria that act like magnets.
49Endospores Resting cells formed for survival Learning objective: Describe the functions of endospores, sporulation, and endospore germination.Resting cells formed for survivalSporulation: Endospore formationResistant to desiccation, heat, chemicalsBacillus, ClostridiumGermination: Return to vegetative state
50Endospores tend to form under conditions of stress.
51Eukaryotic Cells Comparing Prokaryotic and Eukaryotic Cells Prokaryote comes from the Greek words for prenucleus.Eukaryote comes from the Greek words for true nucleus.
56Flagella and CiliaFlagella are few and long (motility), cilia are numerous and short (motility and move substances along cell surface)MicrotubulesTubulin9 pairs + 2 arrangementsFigure 4.23c
57Cell Wall and Glycocalyx Learning objective: Compare and contrast prokaryotic and eukaryotic cell walls and glycocalyxes.Cell wallPlants, algae, some fungi contain celluloseCarbohydratesCellulose, chitin (fungal), glucan & mannan (yeast)Glycocalyx surround animal cells (strength, attachment to other cells)Carbohydrates extending from animal plasma membraneBonded to proteins and lipids in membrane
58Plasma Membrane Phospholipid bilayer in both p. and e. cells Learning objective: Compare and contrast prokaryotic and eukaryotic plasma membranes.Phospholipid bilayer in both p. and e. cellsPeripheral proteinsIntegral proteinsTransmembrane proteinsSterolsGlycocalyx carbohydrates not found in p. cells except Mycoplasma bacteria
59Plasma MembraneSelective permeability allows passage of some moleculesSimple diffusionFacilitative diffusionOsmosisActive transportEndocytosisPhagocytosis: Pseudopods extend and engulf particles (solids)Pinocytosis: Membrane folds inward bringing in fluid and dissolved substances (liquids)
60Eukaryotic CellCytoplasm Substance inside plasma membrane and outside nucleusCytosol Fluid portion of cytoplasmCytoskeleton Microfilaments, intermediate filaments, microtubulesCytoplasmic streaming Movement of cytoplasm throughout cellsLearning objectives:Define organelle.Describe the functions of the nucleus, endoplasmic reticulum, ribosomes, Golgi complex, lysosomes, vacuoles, mitochondria, chloroplasts, peroxisomes, and centrosomes.
61Organelles Specialized membrane-bound structure in cytoplasm: Nucleus Contains chromosomes (DNA)ER Transport network, ribosomesGolgi complex Membrane formation and protein secretionLysosome Digestive enzymesVacuole Brings food into cells and provides supportMitochondrion Cellular respiration (ATP)Chloroplast Photosynthesis (70S ribosomes)Peroxisome Oxidation of fatty acids; destroys H2O2
62Eukaryotic Cell Not membrane-bound: Ribosome Protein synthesis (translation)Centrosome Consists of protein fibers and centriolesCentriole Mitotic spindle formation
64Endoplasmic Reticulum Rough ER contains ribosomes – site of protein translationSmooth ER performs various functions:Synthesizes phospholipids, fats, steroidsIn liver: glucose release and detoxify toxinsCreates vesiclesFigure 4.25
65Ribosomes 80S Membrane-bound Attached to ER Free In cytoplasm 70S In chloroplasts and mitochondria
66Golgi ComplexGolgi complex modifies, sorts, and packages proteins received from the ER; discharges proteins via exocytosis; replaces portions of the plasma membrane; and forms lysosomes (digestive enzymes).Figure 4.26
68Vacuoles (storage of toxins, food, water) Figure 4.22b
69Mitochondrion (furnace of the cell) Site of the Krebs Cycle, which produces the energy currency of the cell - ATPFigure 4.27
70ChloroplastStructure similar to mitochondria – the reverse side of respiration:C6H12O6 + O2 = H2O + CO2 + ATPPhotosynthesis:H2O + CO2 + sun = C6H12O6 + O2Figure 4.28
71Endosymbiotic Theory Learning objective: Discuss evidence that supports the endosymbiotic theory of eukaryotic evolution.Mitochondria and chloroplasts resemble bacteria in size and shape as do their ribosomesThese organelles contain circular DNA like prokaryotes and can reproduce apart from their host cellFigure 10.2