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1、1,Cell Structure and Function,Lecture 1,2,Outline,Cellular Level of OrganizationCell theoryCell sizeProkaryotic CellsEukaryotic CellsOrganellesNucleus and RibosomeEndomembrane SystemOther Vesicles and VacuolesEnergy related organellesCytoskeletonCentrioles,Cilia,and Flagella,3,Cell Theory,Cell was n
2、ot discovered untill the development of MicroscopeDetailed study of the cell began in the 1830s A unifying concept in biologyStates that:All organisms are composed of cellsAll cells come only from preexisting cellsCells are the smallest structural and functional unit of organismsCells carry genetic
3、information in the form of DNA,4,Sizes of Living Things,5,Cell Size,Cells range in size from one millimeter down to one micrometer Cells need a large surface area of plasma membrane to adequately exchange materials.The surfaceareatovolume ratio requires that cells be small,6,Surface to Volume Ratio,
4、7,Microscopy Today:Compound Light Microscope,Light passed through specimenFocused by glass lensesMax magnification about 1000XResolves objects separated by 0.2 mm,500X better than human eyeResolution is limited by the wavelength of light(nanometer),8,Compound Light Microscope,Diaphragm controls amou
5、nt of light important for image contrastCoarse Adjustment Knob focuses the imageFine Adjustment Knob finely focuses the image,9,Microscopy Today:Transmission Electron Microscope,Abbreviated T.E.M.Uses a beam of electrons to allow 100 fold higher magnificationBecause it uses beam of electrons,its res
6、olution is at the atomic level(picometer)Tissue must be fixed and sectionedCan living specimen be examined by T.E.M?,10,Transmission Electron Microscope,11,Microscopy Today:Immunofluorescence Light Microscope,Antibodies developed against a specific proteinFluorescent dye molecule attached to antibod
7、y moleculesSpecimen exposed to fluorescent antibodiesUltra-violet light(black light)passed through specimenFluorescent dye glows in color where antigen is locatedEmitted light is focused by glass lenses onto human retinaAllows mapping distribution of a specific protein in cell,12,Microscopy and Amoe
8、ba proteus,Cells Under the Microscope,phase-contrast light microscope-look at unstained living animal cells.electron microscope-look at organelles e.g.ribosomes.fluorescence microscope-look at a living cell expressing green fluorescent protein or to do confocal microscopy.,Autoradiography,Radioactiv
9、e compounds decay or transform into other compounds or elements.An autoradiograph is an image on an x-ray film or nuclear emulsion produced by the pattern of decay emissions(e.g.,beta particles or gamma rays)from a distribution of a radioactive substanceAutoradiography can also uses radioactive mole
10、cule to study biochemical activity,Protein synthesis,14,15,Cell Fractionation and Differential Centrifugation,Cell fractionation is the breaking apart of cellular componentsDifferential centrifugation:Allows separation of cell partsSeparated out by size&densityWorks like spin cycle of washerThe fast
11、er the machine spins,the smaller the parts that are settled out,16,Cell Fractionation and Differential Centrifugation,Eukaryotes Vs Prokaryotes,17,18,The Structure of Bacteria,Occur in three basic shapes:Spherical coccus,Rod-shaped bacillus,Spiral spirillum(if rigid)or spirochete(if flexible).Cell E
12、nvelope includes:Plasma membrane-lipid bilayer with imbedded and peripheral proteinCell wall-maintains the shape of the cell,19,The Structure of Bacteria,20,The Structure of Bacteria,21,The Structure of Bacteria Cytoplasm&Appendages,CytoplasmSemifluid solutionBounded by plasma membraneContains water
13、,inorganic and organic molecules,and enzymes.Nucleoid is a region that contains the single,circular DNA molecule.Plasmids are small accessory(extrachromosomal)rings of DNAAppendagesFlagella Provide motilityFimbriae small,bristle-like fibers that sprout from the cell surfaceSex pili rigid tubular str
14、uctures used to pass DNA from cell to cell,22,Eukaryotic Cells,Domain Eukarya includes:ProtistsFungiPlantsAnimalsCells contain:Membrane-bound nucleus that houses DNASpecialized organellesPlasma membraneMuch larger than prokaryotic cells Some cells(e.g.,plant cells)have a cell wall,23,Hypothesized Or
15、igin of Eukaryotic Cells,24,Eukaryotic Cells:Organelles,Eukaryotic cells are compartmentalizedThey contain small structures called organellesPerform specific functions Isolates reactions from othersTwo classes of organelles:Endomembrane system:Organelles that communicate with one anotherVia membrane
16、 channelsVia small vesiclesEnergy related organellesMitochondria&chloroplastsBasically independent&self-sufficient,25,Plasma Membrane,26,Animal Cell Anatomy,27,Plant Cell Anatomy,Cytosole,Cytosol,contains many long,fine filaments of protein that are responsible for cell shape and structure and there
17、by form the cells cytoskeleton,28,29,Nucleus,Command center of cell,usually near centerSeparated from cytoplasm by nuclear envelopeConsists of double layer of membraneNuclear pores permit exchange between nucleoplasm&cytoplasmContains chromatin in semifluid nucleoplasmChromatin contains DNA of genes
18、,and proteins(Histones)Condenses to form chromosomesChromosomes are formed during cell division Nucleolus is a dense structure in the nucleusSynthesize ribosome RNA(rRNA),30,Anatomy of the Nucleus,31,Ribosomes,Are the site of protein synthesis in the cellComposed of rRNA and proteinConsists of a lar
19、ge subunit and a small subunitSubunits made in nucleolusMay be located:On the endoplasmic reticulum(thereby making it“rough”),orFree in the cytoplasm,32,Nucleus,Ribosomes,&ER,33,Endomembrane System,Series of intracellular membranes that compartmentalize the cell Restrict enzymatic reactions to speci
20、fic compartments within cellConsists of:Nuclear envelopeMembranes of endoplasmic reticulumGolgi apparatusVesiclesSeveral typesTransport materials between organelles of system,34,Endomembrane System:The Endoplasmic Reticulum,A system of membrane channels and saccules(flattened vesicles)continuous wit
21、h the outer membrane of the nuclear envelope Rough ERStudded with ribosomes on cytoplasmic sideProtein anabolismSynthesizes proteinsModifies and processes proteinsAdds sugar to proteinResults in glycoproteinsSmooth ERNo ribosomesSynthesis of lipidsSite of various synthetic processes,detoxification,a
22、nd storageForms transport vesicles,35,Endoplasmic Reticulum,36,Endomembrane System:The Golgi Apparatus,Golgi ApparatusConsists of flattened,curved sacculesResembles stack of hollow pancakesModifies proteins and lipidsReceives vesicles from ER on cis(or inner face)Modifies them and repackages them in
23、 vesiclesRelease the vesicles from trans(or outer face)Within cellExport from cell(secretion,exocytosis),37,Golgi Apparatus,38,Endomembrane System:Lysosomes,Membrane-bound vesicles(not in plants)Produced by the Golgi apparatusContain powerful digestive enzymes and are highly acidic Digestion of larg
24、e moleculesRecycling of cellular debris and resourcesAutolysis may occur in injured or dying cell to cause apoptosis(programmed cell death,like tadpole losing tail),39,Lysosomes,40,Endomembrane System:Summary,Proteins produced in rough ER and lipids from smooth ER are carried in vesicles to the Golg
25、i apparatus.The Golgi apparatus modifies these products and then sorts and packages them into vesicles that go to various cell destinations.Secretory vesicles carry products to the membrane where exocytosis produces secretions.Lysosomes fuse with incoming vesicles and digest macromolecules.,41,Endom
26、embrane System:A Visual Summary,42,Peroxisomes,Similar to lysosomesMembrane-bounded vesiclesEnclose enzymes that rid the cell of toxic peroxidesParticipate in the metabolism of fatty acids and many other metabolites,43,Peroxisomes,44,Vacuoles,Membranous sacs that are larger than vesiclesStore materi
27、als that occur in excessOthers very specialized(contractile vacuole)Plants cells typically have a central vacuoleUp to 90%volume of some cellsFunctions in:Storage of water,nutrients,pigments,and waste productsDevelopment of turgor pressureSome functions performed by lysosomes in other eukaryotes,45,
28、Vacuoles,46,Energy-Related Organelles:Chloroplast Structure,Bounded by double membraneInner membrane infoldedForms disc-like thylakoids,which are stacked to form granaSuspended in semi-fluid stromaChlorophyllGreen photosynthetic pigmentChlorophyll capture solar energy,47,Energy-Related Organelles:Ch
29、loroplasts,Serve as the site of photosynthesis Captures light energy to drive cellular machineryPhotosynthesisSynthesizes carbohydrates from CO2&H2OMakes own food using CO2 as only carbon sourceInorganic molecules(Energy-poor compounds)are converted to organic molecules(energy-rich compounds)Only pl
30、ants,algae,and certain bacteria are capable of conducting photosynthesis,48,Chloroplast Structure,49,Energy-Related Organelles:Mitochondria,Smaller than chloroplastContain ribosomes and their own DNA Surrounded by a double membrane Inner membrane surrounds the matrix and is convoluted(folds)to form
31、cristae.Matrix Inner semifluid containing respiratory enzymesBreak down carbohydrates Involved in cellular respirationProduce most of ATP utilized by the cellContain their own DNA and ribosome i.e.they are semiautonomousInherited from Oocyte,50,Mitochondrial Structure,Mitochondrial Origin Hypothesis
32、,51,52,The Cytoskeleton,Maintains cell shapeAssists in movement of cell and organellesAids movement of materials in and out of cellsThree types of macromolecular fibersMicrofilamentIntermediate FilamentsMicrotubulesAssemble and disassemble as needed,53,The Cytoskeleton:Actin Filaments,Microfilament
33、are rods of actinExtremely thin filaments like twisted pearl necklaceSupport for microvilli in intestinal cellsIntracellular traffic controlFor moving stuff around within cellCytoplasmic streamingFunction in pseudopods of amoeboid cellsImportant component in muscle contraction,54,The Cytoskeleton:Ac
34、tin Filament Operation,55,The Cytoskeleton:Intermediate Filaments,Intermediate in size between actin filaments and microtubulesRope-like assembly of fibrous polypeptidesFunctions:Support nuclear envelopeCell-cell junctions,like those holding skin cells tightly together,56,The Cytoskeleton:Microtubul
35、es,Hollow cylinders made of two globular proteins called a and b tubulinSpontaneous pairing of a and b tubulin molecules form structures called dimersDimers then arrange themselves into tubular spirals of 13 dimers aroundAssembly:Under control of Microtubule Organizing Center(MTOC)Most important MTO
36、C is centrosomeFunction:Provide framework for movement of organelle within cellDirect separation of chromosomes during cell division(e.g.Centrioles are composed of microtubules)Provide locomotion and movement(e.g.flagella and cilia),57,The Cytoskeleton:Microtubule Operation,58,The Cytoskeleton,59,Mi
37、crotubular Arrays:Centrioles,Short,hollow cylindersOne pair per animal cellLocated in centrosome of animal cellsOriented at right angles to each otherSeparate during mitosis to determine plane of division,60,Cytoskeleton:Centrioles,61,Microtubular Arrays:Cilia and Flagella,Hair-like projections from
38、 cell surface that aid in cell movementIn eukaryotes,cilia are much shorter than flagellaCilia move in coordinated waves like oarsFlagella move like a propeller or cork screw,62,Structure of a Flagellum,63,Comparison of Prokaryotic and Eukaryotic Cells,64,Membrane Structure and Function,Lecture 1,65
39、,Outline,Membrane ModelsFluid-MosaicPlasma Membrane Structure and FunctionPhospholipidsProteinsPlasma Membrane PermeabilityDiffusionOsmosisTransport Via Carrier ProteinsCell Surface Modifications,66,Structure and Function:The Phospholipid Bilayer,The plasma membrane is common to all cellsSeparates:I
40、nternal living cytoplasmic fromExternal environment of cellPhospholipid bilayer:External surface lined with hydrophilic polar headsCytoplasmic surface lined with hydrophilic polar headsNonpolar,hydrophobic,fatty-acid tails sandwiched in between,67,Unit Membrane,68,Membrane Models,Fluid-Mosaic ModelT
41、hree components:Basic membrane referred to as phospholipid bilayerProtein moleculesFloat around like icebergs on a seaMembrane proteins may be peripheral or integralPeripheral proteins are found on the inner membrane surfaceIntegral proteins are partially or wholly embedded(transmembrane)in the memb
42、raneSome have carbohydrate chains attachedCholesterol,69,The Fluid Mosaic Model,70,Transmembrane Proteins,71,Functions of Membrane Proteins,Channel Proteins:TubularAllow passage of molecules through membraneCarrier Proteins:Combine with substance to be transportedAssist passage of molecules through
43、membraneCell Recognition Proteins:Provides unique chemical ID for cellsHelp body recognize foreign substancesReceptor Proteins:Binds with messenger moleculeCauses cell to respond to messageEnzymatic Proteins:Carry out metabolic reactions directly,72,Membrane Protein Diversity,73,Science Focus:Cell S
44、ignaling,74,Types of Transport:Active vs.Passive,Plasma membrane is differentially(selectively)permeable Allows some material to passInhibits passage of other materialsPassive Transport:No ATP requirementMolecules follow concentration gradientActive TransportRequires carrier proteinRequires energy i
45、n form of ATP,75,Passage of Molecules Across the Membrane,76,Types of Membrane Transport:Overview,77,Types of Transport:Diffusion,A solution consists of:A solvent(liquid),andA solute(dissolved solid)DiffusionNet movement of solute molecules down a concentration gradientMolecules move both ways along
46、 gradientMolecules move from high to low Equilibrium:When NET change stopsSolute concentration uniform no gradient,78,Gas Exchange in Lungs:Diffusion Across Lung,79,Types of Transport:Osmosis,Osmosis:Special case of diffusionFocuses on solvent(water)movement rather than soluteDiffusion of water acro
47、ss a differentially(selectively)permeable membraneSolute concentration on one side high,but water concentration lowSolute concentration on other side low,but water concentration highWater diffuses both ways across membrane but solute cantNet movement of water is toward low water(high solute)concentr
48、ationOsmotic pressure is the pressure that develops due to osmosis,80,Types of Transport:Carrier Proteins,Facilitated TransportSmall moleculesCant get through membrane lipidsCombine with carrier proteinsFollow concentration gradientActive TransportSmall moleculesMove against concentration gradientCo
49、mbining with carrier proteinsRequires energy,81,Types of Transport:Carrier Proteins,Facilitated TransportSmall moleculesCant get through membrane lipidsCombine with carrier proteinsFollow concentration gradientActive TransportSmall moleculesMove against concentration gradientCombining with carrier p
50、roteinsRequires energy,82,Types of Transport:Membrane-Assisted Transport,Macromolecules transported into or out of the cell inside vesiclesExocytosis Vesicles fuse with plasma membrane and secrete contentsEndocytosis Cells engulf substances into pouch which becomes a vesiclePhagocytosis Large,solid
