Functional Anatomy of Prokaryotic and Eukaryotic CellsChapter 3 Part B

Q&APenicillin was called a miracle drug because it doesnt harm human cells. Why doesnt it?

Prokaryotic and Eukaryotic CellsProkaryote comes from the Greek words for prenucleus.Eukaryote comes from the Greek words for true nucleus.

ProkaryoteSize 1-10 micronsOne circular chromosome, not in a membraneNo histonesNo organellesPeptidoglycan cell walls if BacteriaPseudomurein cell walls if ArchaeaBinary fissionEukaryoteSize 10-100 micronsPaired chromosomes, in nuclear membraneHistones OrganellesPolysaccharide cell wallsMitotic spindle

The Prokaryotic Cell(a)PilusRibosomesCapsule(b)CytoplasmCytoplasmicmembraneCell wallFlagellumCell wallChromosome(DNA)Nucleoid0.5 mCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(b): Courtesy of L. Santo, H. Hohl, and H. Frank, "Ultrastructure of Putrefactive Anaerobe 3679h During Sporulation, Journal of Bacteriology 99:824, 1969. American Society for Microbiology;

Figures 4.1a, 4.2a, 4.2d, 4.4a, 4.4b, 4.4cBasic ShapesBacillus (rod-shaped) Coccus (spherical)SpiralSpirillumVibrioSpirochete

Most prokaryotes divide by binary fissionCells often stick together following divisionForm characteristic groupingsExamples:Neisseria gonorrhoeae (diplococcus)Streptococcus (long chains)Sarcina (cubical packets)Staphylococcus (grapelike clusters)GroupingsCell dividesin one plane.DiplococcusChainsChain of cocciPackets(a)PacketClusters(b)Cell dividesin two or more planesperpendicular to oneanotherClusterCell dividesin several planes atrandom.(c)Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(a): (top): George Musil/Visuals Unlimited; : (bottom): David M. Phillips/Visuals Unlimited; (b): R. Kessel & C. Shih/Visuals Unlimited; (c): Oliver Mecks/Photo Researchers, Inc.

Average size: 0.2 -1.0 m 2 - 8 mBasic shapes:

Unusual shapesStar-shaped StellaSquare HaloarculaMost bacteria are monomorphicA few are pleomorphicFigure 4.5

Figures 4.1a, 4.1d, 4.2b, 4.2cArrangementsPairs: Diplococci, diplobacilli

Clusters: Staphylococci

Chains: Streptococci, streptobacilli

Figure 24.12GlycocalyxOutside cell wallUsually stickyCapsule: neatly organizedSlime layer: unorganized and loose Extracellular polysaccharide allows cell to attachCapsules prevent phagocytosis

Figure 4.8bFlagella

Outside cell wallMade of chains of flagellinAttached to a protein hookAnchored to the wall and membrane by the basal bodyHelicobacter pylori electron micrograph, showing multiple flagella on the cell surface (negative staining).

Figure 4.7Arrangements of Bacterial Flagella

E. coliOutbreak that was associated with contaminated Dole brand Baby Spinach and resulted in 205 confirmed illnesses and three deaths. The organism E.coli O157:H7 Potential environmental risk factors for E.coli O157:H7, the proximity of irrigation wells used to grow produce for ready-to-eat packaging, and surface waterways exposed to feces from cattle and wildlife. What kind of flagella?

Axial FilamentsEndoflagellaIn spirochetesAnchored at one end of a cellRotation causes the entire bacterium to move forward in a corkscrew-like motion. Treponema pallidum the causitive agent of Syphillus

corkscrew motion allows it to move in a through viscous mediums such as mucus. It gains access to host's blood and lymph systems through tissue and mucus membranes Figure 4.10a

ChemotaxisBacteria sense chemicals and move accordinglyNutrients may attract, toxins may repelMovement is series of runs and tumblesOther responses observedAerotaxisMagnetotaxisThermotaxisPhototaxis3.8. Filamentous Protein AppendagesTTRRTThe cell moves randomlywhen there is noConcentration gradient ofattractant or repellent.When a cell senses it is moving to wardan attractant, it tumbles (T) less frequently,resulting in longer runs (R).Gradient of attractant concentrationTumble (T)Tumble (T)A cell moves via a series of run sand tumbles.Run (R)Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.0.4 mmMagnetite particlesFlagellumCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. D. Blackwill and D. Maratea/Visuals UnlimitedTCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Pili are shorter than flagellaTypes that allow surface attachment termed fimbriaeTwitching motility, gliding motility involve piliSex pilus used to join bacteria for DNA transfer3.8. Filamentous Protein AppendagesEpithelial cellBacteriumBacteriumwith pili(b)(a)Sex pilusFlagellumOther pili1 m5 mCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(a): Courtesy of Dr. Charles Brinton, Jr.; (b): U.S. Department of Agriculture/Harley W. Moon;

Fimbriae allow attachmentPili are used to transfer DNA from one cell to anotherThe terms pilus and fimbria are often used interchangeably, although some researchers reserve the term pilus for the sexual appendage required for bacterial conjugation. E.coli transferring genetic materialFigure 4.11

Figure 4.11Fimbriae and PiliFimbriae allow attachment

Cell wall is strong, rigid structure that prevents cell lysisArchitecture distinguishes two main types of bacteriaGram-positiveGram-negativeMade from peptidoglycanFound only in bacteria3.6. Cell Wall

Cell WallSemi rigid structure responsible for the shapeSurrounds the plasma membrane and protects the cell from outside environment. Prevents osmotic lysisMade of peptidoglycan (in bacteria)site of action of some antibioticsImportant because it may contribute to some species to cause disease Figure 4.6a, b

Peptidoglycan in Gram-Positive BacteriaPolymer of disaccharide:N-acetylglucosamine (NAG) N-acetylmuramic acid (NAM)Linked by polypeptides

Cell wall is made from peptidoglycanAlternating series of subunits form glycan chainsN-acetylmuramic acid (NAM)N-acetylglucosamine (NAG)Tetrapeptide chain (string of four amino acids) links glycan chains

3.6. Cell WalleGlycanchainTetrapeptidechain(amino acids)Glycan chains are composed ofAlternating subunits of NAG andNAM. They are cross-linked viaTheir tetrapeptide chainsto Create peptidoglycan.GlycanchainN-acetylmuramic acid(NAM)N-acetylglucosamin(NAG)Chemical structure of N-acetylglucosamine (NAG)and N-acetylmuramic acid (NAM); the ring structureof each molecule is glucose.NAMTetrapeptide chain(amino acids)Peptide interbridgeInterconnected glycan chainsform a large sheet. Multipleconnected layers create athree-dimensional molecule.Peptide interbridge(Gram-positive cells)NAGNAGNAMNAGNAMNAGNAMNAGNAMOOOHHHHHHOOCOCOCOHCH2OHCH2OHHCNHNHCH3CH3OHCH3HOOHPeptidoglycanCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Gram-positive cell wall has thick peptidoglycan layerThe Gram-Positive Cell Wall(a)(c)CytoplasmicmembranePeptidoglycanGram-positive(b)Gel-likematerialPeptidoglycanand teichoic acidsCytoplasmicmembraneCytoplasmicmembranePeptidoglycan(cell wall)Gel-likematerialN-acetylglucosamineN-acetylmuramic acidTeichoic acid0.15 mCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(c): Terry Beveridge, University of Guelph

Gram-Positive Bacterial Cell WallFigure 4.13b

Gram-Negative Bacterial Cell WallFigure 4.13c

Gram-negative cell wall has thin peptido-glycan layerOutside is unique outer membraneThe Gram-Negative Cell WallLipoproteinPeptidoglycan(a)PeptidoglycanCytoplasmicmembrane(d)Lipopolysaccharide(LPSPorin proteinOutermembrane(lipid bilayer)PeriplasmCytoplasmicmembrane(inne rmembrane;lipid bilayer)PeptidoglycanOutermembranePeriplasmCytoplasmicmembrane(c)PeriplasmOutermembraneLipid ACore polysaccharideO antigen(varies in length andcomposition)0.15 m(b)Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(d): Terry Beveridge, University of Guelph

Gram-positiveCell WallThick peptidoglycanTeichoic acidsFigure 4.13bcThin peptidoglycanOuter membranePeriplasmic spaceGram-positive Cell Wall

Figure 4.13bGram-Positive Cell WallsTeichoic acidsLipoteichoic acid links to plasma membraneWall teichoic acid links to peptidoglycanMay regulate movement of cationsPolysaccharides provide antigenic variation

Gram-Negative Outer MembraneProtection from phagocytes, complement, and antibioticsO polysaccharide antigen, e.g., E. coli O157:H7Lipid A is an endotoxinPorins (proteins) form channels through membrane

Figure 4.13cGram-Negative Cell WallLipopolysaccharides, lipoproteins, phospholipidsForms the periplasm between the outer membrane and the plasma membrane

Gram-PositiveCell Wall2-ring basal bodyDisrupted by lysozymePenicillin sensitiveFigure 4.13bc4-ring basal bodyEndotoxinTetracycline sensitiveGram-Negative Cell Wall

Gram Stain MechanismCrystal violet-iodine crystals form in cellGram-positiveAlcohol dehydrates peptidoglycanCV-I crystals do not leaveGram-negativeAlcohol dissolves outer membrane and leaves holes in peptidoglycanCV-I washes out

Figure 24.8Atypical Cell WallsAcid-fast cell wallsLike gram-positiveWaxy lipid (mycolic acid) bound to peptidoglycanMycobacteriumNocardia

Atypical Cell WallsMycoplasmasLack cell wallsSterols in plasma membraneArchaeaWall-less orWalls of pseudomurein (lack NAM and D-amino acids)

Damage to the Cell WallLysozyme digests disaccharide in peptidoglycanPenicillin inhibits peptide bridges in peptidoglycanProtoplast is a wall-less cellSpheroplast is a wall-less gram-positive cellProtoplasts and spheroplasts are susceptible to osmotic lysisL forms are wall-less cells that swell into irregular shapes

Figure 4.14aThe Plasma Membrane

PhospholipidbilayerHydrophilic headHydrophobic tailProteinsCytoplasmic membrane defines boundary of cellPhospholipid bilayer embedded with proteinsHydrophobic tails face in; hydrophilic tails face outServes as semipermeable membraneProteins serve numerous functionsSelective gatesSensors of environmentalconditionsFluid mosaic model: proteins drift about inlipid bilayer3.4. The Cytoplasmic MembraneCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Plasma Membrane & Fluid Mosaic ModelPhospholipid bilayer Peripheral, Integral, & Transmembrane proteinsMembrane is as viscous as olive oil.Proteins move to functionPhospholipids rotate and move laterally

Figure 4.14b

Cytoplasmic membrane is selectively permeableO2, CO2, N2, small hydrophobic molecules, and water pass freelySome cells facilitate water passage with aquaporinsOther molecules must be moved across membrane via transport systemsPermeability of Lipid Bilayer(a) The cytoplasmic membrane is selectively permeable. Gases, small hydrophobic molecules, and water are the only substances that pass freely through the phospholipid bilayer.(b) Aquaporins allow water to pass through the cytoplasmic membrane more easily.Passes through:WaterDo not pass through:SugarsIonsAmino acidsATPMacromoleculesWaterAquaporinPass through easily:Gases (O2, CO2, N2)Small hydrophobicmoleculesCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Plasma MembraneSelective permeability allows passage of some moleculesEnzymes for ATP productionPhotosynthetic pigments on foldings called chromatophores or thylakoids

The Plasma MembraneDamage to the membrane by alcohols, quaternary ammonium (detergents), and polymyxin antibiotics causes leakage of cell contents

Movement Across MembranesSimple 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.

Figure 4.17

Water flows across amembrane toward thehypertonic solution.Hypotonic solutionHypertonic solutionSolute moleculeWater flows inCytoplasmic membrane isforced against cell wall.Cytoplasmic membranepulls away from cell wall.Water flows outWater flowWater flowSimple DiffusionMovement from high to low concentrationSpeed depends on concentrationOsmosisDiffusion of water across selectively permeable membrane due to unequal solute concentrationsThree terms:HypertonicIsotonicHypotonicPermeability of Lipid BilayerCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Movement of Materials across MembranesSimple diffusion: Movement of a solute from an area of high concentration to an area of low concentration

Facilitated diffusion: Solute combines with a transporter protein in the membrane

Figure 4.18aMovement of Materials across MembranesOsmosis: The movement of water across a selectively permeable membrane from an area of high water to an area of lower water concentrationOsmotic pressure: The pressure needed to stop the movement of water across the membrane

Figure 4.18ceThe Principle of Osmosis

Most molecules must pass through proteins functioning as selective gatesTermed transport systemsProteins may be called permeases, carriersMembrane-spanningHighly specific: carriers transport certain molecule type3.5. Directed Movement of Molecules Across Cytoplasmic Membrane1Transport protein recognizesa specific molecule.2Binding of that molecule changesthe shape of the transport protein.3The molecule is released on theother side of the membrane.Small moleculeCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Facilitated diffusion is a form of passive transportMovement down gradient; no energy requiredNot typically useful in low-nutrient environmentsActive transport requires energyMovement against gradientTwo main mechanismsUse proton motive forceUse ATP (ABC transporter)Group TranslocationChemically alter compoundPhosphorylation commonGlucose, for example3.5. Directed Movement of Molecules Across Cytoplasmic Membrane

Movement of Materials across MembranesActive transport: Requires a transporter protein and ATPGroup translocation: Requires a transporter protein and PEP

Figure 4.6CytoplasmThe substance inside the plasma membrane

Figure 4.6The NucleoidBacterial chromosome

Chromosome forms gel-like region: the nucleoidSingle circular double-stranded DNAPacked tightly via binding proteins and supercoilingPlasmids are circular, supercoiled, dsDNAUsually much smaller; few to several hundred genesMay share with other bacteria; antibiotic resistance can spread this way3.9. Internal Structures(a)0.5 m(b)1.3 mDNACopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(a): CNRI/SPL/Photo Researchers, Inc.; (b): Dr. Gopal Murti/SPL/Photo Researchers

The Prokaryotic Cell(a)PilusRibosomesCapsule(b)CytoplasmCytoplasmicmembraneCell wallFlagellumCell wallChromosome(DNA)Nucleoid0.5 mCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(b): Courtesy of L. Santo, H. Hohl, and H. Frank, "Ultrastructure of Putrefactive Anaerobe 3679h During Sporulation, Journal of Bacteriology 99:824, 1969. American Society for Microbiology;

Figure 4.6Ribosomes

Figure 4.19The Prokaryotic RibosomeProtein synthesis70S50S + 30S subunits

Cytoskeleton: internal protein frameworkOnce thought bacteria lacked thisBacterial proteins similar to eukaryotic cytoskeleton have been characterizedLikely involved in cell division and controlling cell shapeStorage granules: accumulations of polymersSynthesized from nutrients available in excessE.g., carbon, energy storage:GlycogenPoly--hydroxybutyrateGas vesicles: controlledto provide buoyancy3.9. Internal StructuresStorage granules0.5 mCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Courtesy of Dr. Edwin S. Boatman

EndosporesResting cellsResistant to desiccation, heat, chemicalsBacillus, ClostridiumSporulation: Endospore formationGermination: Return to vegetative state

Sporulation triggered by carbon, nitrogen limitationStarvation conditions begin 8-hour processEndospore layers prevent damageExclude molecules (e.g., lysozyme)Cortex maintains core in dehydrated state, protects from heatCore has small proteins that bind and protect DNACalcium dipicolinate seems to play important protective roleGermination triggered by heat, chemical exposure3.9. Internal Structures54123Peptidoglycan-containingMaterial is laid down betweenthe two membranes that nowsurround the forespore.Vegetative growth stops;DNA is duplicated.A septum forms, dividingthe cell asymmetrically.The larger compartmentEngulfs the smallercompartment, forming aforespore with in aMother cell.The mother cell is degradedAnd the endospore released.ForesporePeptidoglycan-containingmaterialCore wallCortexSporecoatMother cellCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Formation of Endospores by SporulationFigure 4.21a

Eukaryotic cells larger than prokaryotic cellsInternal structures far more complexHave abundance of membrane-enclosed compartments termed organellesAnimal, plant cells share similarities, have differences

The Eukaryotic CellNucleusNuclear envelopeNucleolusPlasma membraneCentrioleMitochondrionCytoskeleton Actin filamentMicrotubuleIntermediatefilament(a)LysosomePeroxisomeGolgiapparatusRibosomesSmoothendoplasmicreticulumRoughendoplasmicreticulumwithribosomesCytoplasmRoughendoplasmicreticulumWith ribosomesSmoothendoplasmicreticulumRibosomesGolgiapparatusCentralvacuoleChloroplast(opened toshow thylakoids)Adjacent cell wallCell wallPlasma membrane(b)CytoplasmMitochondrionPeroxisomeActinfilamentMicrotubuleIntermediatefilamentNucleolusNuclear envelopeCytoskeletonNucleusCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Figure 4.22aThe Eukaryotic Cell

Figure 4.23a-bFlagella and Cilia

Flagella and cilia appear to project out of cellCovered by extensions of plasma membraneComprised of microtubules in 9 + 2 arrangement3.12. Protein Structures Within the CellFlagella function in motilityVery different than prokaryotic flagellaPropel via whiplike motion or thrash back and forth to pull cell forwardCilia are shorter, move synchronouslyCan move cell forward or move material past stationary cellMicrotubuletripletFlagellumOutermicrotubule pairCentralmicrotubule pairBasal bodyPlasmamembraneCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

The Cell Wall and GlycocalyxCell wallPlants, algae, fungiCarbohydratesCellulose, chitin, glucan, mannanGlycocalyxCarbohydrates extending from animal plasma membraneBonded to proteins and lipids in membrane

Q&APenicillin was called a miracle drug because it doesnt harm human cells. Why doesnt it?

EukaryotesPlasma Membrane Phospholipid bilayerSelective permeability allows passage of some moleculesSimple diffusionFacilitative diffusionOsmosisActive transportEndocytosisPhagocytosis: Pseudopods extend and engulf particlesPinocytosis: Membrane folds inward bringing in fluid and dissolved substancesThe Cell

Plasma membrane similar to prokaryotic cellsPhospholipid bilayer embedded with proteinsBut: layer facing cytoplasm differs from that facing outsideProteins in outer layer serve as receptorsBind specific molecule termed ligandImportant in cell communicationMembranes of many eukaryotes contain sterolsProvide strength to otherwise fluid structureCholesterol in mammals, ergosterol in fungiLipid rafts: allow cell to detect, respond to signalsMany viruses use to enter, exit cellsElectrochemical gradient maintained via sodium or proton pumpsMembrane not involved in ATP synthesisMitochondria perform3.10. The Plasma Membrane

Eukaryotic CellCytoplasmSubstance inside plasma membrane and outside nucleusCytosolFluid portion of cytoplasmCytoskeletonMicrofilaments, intermediate filaments, microtubulesCytoplasmic streamingMovement of cytoplasm throughout cells

Cytoskeleton: cell frameworkActin filaments allow movementPolymers of actin polymerize and depolymerizeMicrotubules are thickest componentLong hollow structures made from tubulinMake up mitotic spindlesCilia, flagellaFramework for organelle and vesicle movementIntermediate filaments provide mechanical support3.12. Protein Structures Within the CellMicrotubuleIntermediate filamentActin filamentPlasma membrane(a)Actin filamentMicrotubule(b)(c)Intermediate filamentCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Organelles compartmentalize functionsVesicles can transport compounds betweenBuds off from organelle, fuses with membrane of anotherThe Eukaryotic CellCellmembraneNucleusNuclearmembraneMitochondrion1 m(c)Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.(c): Courtesy of Thomas FritscheA vesicle forms when asection of an organellebuds off.The mobile vesicle can then move toother parts of the cell, ultimately fusingwith the membrane of another organelle.ProteinBuddingvesicleMigratingtransportvesicleFusingvesicleCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

OrganellesMembrane-bound:NucleusContains chromosomesERTransport networkGolgi complex Membrane formation and secretionLysosomeDigestive enzymesVacuoleBrings food into cells and provides supportMitochondrion Cellular respirationChloroplastPhotosynthesisPeroxisomeOxidation of fatty acids; destroys H2O2

Figure 4.24The Eukaryotic Nucleus

Rough Endoplasmic ReticulumEndoplasmic reticulum (ER)System of flattened sheets, sacs, tubes

Rough ER dotted with ribosomesSynthesize proteins not destined for cytoplasm

Smooth ER: lipid synthesis and degradation

Figure 4.26Golgi ComplexThe Golgi ApparatusMembrane-bound flattened compartmentsMacromolecules synthesized in ER are modifiedAddition of carbohydrate, phosphate groups

Lysosomes contain degradative enzymesCould destroy cell if not containedEndosomes, phagosomes fuse with lysosomesMaterial taken up by cell is degradedSimilarly, old organelles, vesicles can fuse: autophagyPeroxisomes use O2 to degrade lipids, detoxify chemicalsEnzymes generate hydrogen peroxide, superoxidePeroxisome contains and ultimately degradesProtects cell from toxic effects3.13. Membrane-Bound Organelles

Figure 4.22bLysosomes and Vacuoles

Figure 4.22bPeroxisome and Centrosome

Figure 4.27MitochondriaMitochondria generate ATPBounded by two lipid bilayersMitochondrial matrix contains DNA, 70S ribosomes

Figure 4.28ChloroplastsChloroplasts are site of photosynthesisFound only in plants, algaeHarvest sunlight to generate ATPATP used to convert CO2 to sugar and starch

Endosymbiotic theory: ancestors of mitochondria and chloroplasts were bacteriaResided in other cells in mutually beneficial partnershipEach partner became indispensable to the otherEndosymbiont lost key features (cell wall, replication)Several lines of evidence supportMitochondria, chloroplasts carry DNA for some ribosomal proteins, ribosomal RNA for 70S ribosomesNuclear DNA encodes some partsDouble membrane surrounds bothPresent-day endosymbionts similarly retainDivision is by binary fissionMitochondrial DNA sequences comparable to obligate intracellular parasites: rickettsias

The Origins of Mitochondria and Chloroplasts

Figure 10.2Endosymbiotic Theory

*****Outside cell wallsugar coat ~polysaccharideUsually stickyIf the substance is organized and is firmly attached to the cell wall, the glycocalyx is descirbed as a capsuleA capsule is neatly organizedIf the substance is unorganized the glycocalyx is described a a slime layerA slime layer is unorganized & loosely attachedExtracellular polysaccharide allows cell to attachCapsules prevent phagocytosisPotential environmental risk factors for E.coli O157:H7 contamination at or near the field included the presence of wild pigs, the proximity of irrigation wells used to grow produce for ready-to-eat packaging, and surface waterways exposed to feces from cattle and wildlife**********************************