1、MCAT Prep Exam PowerPoint Lecture Slides are prepared by Dr.Isaac Barjis,Biology Instructor1Cell Structure and Function Lecture 12OutlinelCellular Level of OrganizationlCell theorylCell sizelProkaryotic CellslEukaryotic CellslOrganelleslNucleus and RibosomelEndomembrane SystemlOther Vesicles and Vac
2、uoleslEnergy related organelleslCytoskeletonlCentrioles,Cilia,and Flagella3Cell TheorylCell was not discovered untill the development of MicroscopelDetailed study of the cell began in the 1830s lA unifying concept in biologylStates that:lAll organisms are composed of cellslAll cells come only from p
3、reexisting cellslCells are the smallest structural and functional unit of organismslCells carry genetic information in the form of DNA 4Sizes of Living Things5Cell SizelCells range in size from one millimeter down to one micrometer lCells need a large surface area of plasma membrane to adequately ex
4、change materials.lThe surface area to volume ratio requires that cells be small 6Surface to Volume Ratio7Microscopy Today:Compound Light MicroscopelLight passed through specimenlFocused by glass lenseslMax magnification about 1000XlResolves objects separated by 0.2 mm,500X better than human eyelReso
5、lution is limited by the wavelength of light(nanometer)8Compound Light MicroscopelDiaphragm controls amount of light important for image contrastlCoarse Adjustment Knob focuses the imagelFine Adjustment Knob finely focuses the image9Microscopy Today:Transmission Electron MicroscopelAbbreviated T.E.M
6、.lUses a beam of electrons to allow 100 fold higher magnificationlBecause it uses beam of electrons,its resolution is at the atomic level(picometer)lTissue must be fixed and sectionedlCan living specimen be examined by T.E.M?10Transmission Electron Microscope11Microscopy Today:Immunofluorescence Lig
7、ht MicroscopelAntibodies developed against a specific proteinlFluorescent dye molecule attached to antibody moleculeslSpecimen exposed to fluorescent antibodieslUltra-violet light(black light)passed through specimenlFluorescent dye glows in color where antigen is locatedlEmitted light is focused by
8、glass lenses onto human retinalAllows mapping distribution of a specific protein in cell12Microscopy and Amoeba proteusCells Under the Microscopelphase-contrast light microscope-look at unstained living animal cells.lelectron microscope-look at organelles e.g.ribosomes.lfluorescence microscope-look
9、at a living cell expressing green fluorescent protein or to do confocal microscopy.AutoradiographylRadioactive compounds decay or transform into other compounds or elements.lAn autoradiograph is an image on an x-ray film or nuclear emulsion produced by the pattern of decay emissions(e.g.,beta partic
10、les or gamma rays)from a distribution of a radioactive substancelAutoradiography can also uses radioactive molecule to study biochemical activity,Protein synthesis1415Cell Fractionation and Differential CentrifugationlCell fractionation is the breaking apart of cellular componentslDifferential centr
11、ifugation:lAllows separation of cell partslSeparated out by size&densitylWorks like spin cycle of washerlThe faster the machine spins,the smaller the parts that are settled out16Cell Fractionation and Differential CentrifugationEukaryotes Vs ProkaryotesEukaryotic CellsProkaryotic CellsThe cells of“c
12、omplex”organisms,including all plants,Protists,fungi and animals“Simple”organisms,including bacteria and cyanobacteria(blue-green algae)Contain a nucleus and membrane bound organelles Lack a nucleus and other membrane-encased organelles.Can specialize for certain functions,such as absorbing nutrient
13、s from food or transmitting nerve impulses;multicellular organs and organismsUsually exist as single,virtually identical cellsCell Wall present in Plants and Fungi onlyRibosome:40s,60SCell WallRibosome:30S,50S1718The Structure of Bacteria lOccur in three basic shapes:lSpherical coccus,lRod-shaped ba
14、cillus,lSpiral spirillum(if rigid)or spirochete(if flexible).lCell Envelope includes:lPlasma membrane-lipid bilayer with imbedded and peripheral proteinlCell wall-maintains the shape of the cell19The Structure of Bacteria 20The Structure of Bacteria21The Structure of Bacteria Cytoplasm&AppendageslCy
15、toplasmlSemifluid solutionlBounded by plasma membranelContains water,inorganic and organic molecules,and enzymes.lNucleoid is a region that contains the single,circular DNA molecule.lPlasmids are small accessory(extrachromosomal)rings of DNAlAppendageslFlagella Provide motilitylFimbriae small,bristl
16、e-like fibers that sprout from the cell surfacelSex pili rigid tubular structures used to pass DNA from cell to cell22Eukaryotic CellslDomain Eukarya includes:lProtistslFungilPlantslAnimalslCells contain:lMembrane-bound nucleus that houses DNAlSpecialized organelleslPlasma membranelMuch larger than
17、prokaryotic cells lSome cells(e.g.,plant cells)have a cell wall 23Hypothesized Origin of Eukaryotic Cells24Eukaryotic Cells:OrganelleslEukaryotic cells are compartmentalizedlThey contain small structures called organelleslPerform specific functions lIsolates reactions from otherslTwo classes of orga
18、nelles:lEndomembrane system:lOrganelles that communicate with one anotherlVia membrane channelslVia small vesicleslEnergy related organelleslMitochondria&chloroplastslBasically independent&self-sufficient25Plasma Membrane26Animal Cell Anatomy27Plant Cell AnatomyCytosolelCytosol,contains many long,fi
19、ne filaments of protein that are responsible for cell shape and structure and thereby form the cells cytoskeleton2829NucleuslCommand center of cell,usually near centerlSeparated from cytoplasm by nuclear envelopelConsists of double layer of membranelNuclear pores permit exchange between nucleoplasm&
20、cytoplasmlContains chromatin in semifluid nucleoplasmlChromatin contains DNA of genes,and proteins(Histones)lCondenses to form chromosomeslChromosomes are formed during cell division lNucleolus is a dense structure in the nucleuslSynthesize ribosome RNA(rRNA)30Anatomy of the Nucleus31RibosomeslAre t
21、he site of protein synthesis in the celllComposed of rRNA and proteinlConsists of a large subunit and a small subunitlSubunits made in nucleoluslMay be located:lOn the endoplasmic reticulum(thereby making it“rough”),orlFree in the cytoplasm32Nucleus,Ribosomes,&ER33Endomembrane SystemlSeries of intra
22、cellular membranes that compartmentalize the cell lRestrict enzymatic reactions to specific compartments within celllConsists of:lNuclear envelopelMembranes of endoplasmic reticulumlGolgi apparatuslVesicleslSeveral typeslTransport materials between organelles of system34Endomembrane System:The Endop
23、lasmic ReticulumlA system of membrane channels and saccules(flattened vesicles)continuous with the outer membrane of the nuclear envelope lRough ERlStudded with ribosomes on cytoplasmic sidelProtein anabolismlSynthesizes proteinslModifies and processes proteinslAdds sugar to proteinlResults in glyco
24、proteinslSmooth ERlNo ribosomeslSynthesis of lipidslSite of various synthetic processes,detoxification,and storagelForms transport vesicles 35Endoplasmic Reticulum36Endomembrane System:The Golgi ApparatuslGolgi ApparatuslConsists of flattened,curved sacculeslResembles stack of hollow pancakeslModifi
25、es proteins and lipidslReceives vesicles from ER on cis(or inner face)lModifies them and repackages them in vesicleslRelease the vesicles from trans(or outer face)lWithin celllExport from cell(secretion,exocytosis)37Golgi Apparatus38Endomembrane System:LysosomeslMembrane-bound vesicles(not in plants
26、)lProduced by the Golgi apparatuslContain powerful digestive enzymes and are highly acidic lDigestion of large moleculeslRecycling of cellular debris and resourceslAutolysis may occur in injured or dying cell to cause apoptosis(programmed cell death,like tadpole losing tail)39Lysosomes40Endomembrane
27、 System:SummarylProteins produced in rough ER and lipids from smooth ER are carried in vesicles to the Golgi apparatus.lThe Golgi apparatus modifies these products and then sorts and packages them into vesicles that go to various cell destinations.lSecretory vesicles carry products to the membrane w
28、here exocytosis produces secretions.lLysosomes fuse with incoming vesicles and digest macromolecules.41Endomembrane System:A Visual Summary42PeroxisomeslSimilar to lysosomeslMembrane-bounded vesicleslEnclose enzymes that rid the cell of toxic peroxideslParticipate in the metabolism of fatty acids an
29、d many other metabolites43Peroxisomes44VacuoleslMembranous sacs that are larger than vesicleslStore materials that occur in excesslOthers very specialized(contractile vacuole)lPlants cells typically have a central vacuolelUp to 90%volume of some cellslFunctions in:lStorage of water,nutrients,pigment
30、s,and waste productslDevelopment of turgor pressurelSome functions performed by lysosomes in other eukaryotes45Vacuoles46Energy-Related Organelles:Chloroplast StructurelBounded by double membranelInner membrane infoldedlForms disc-like thylakoids,which are stacked to form granalSuspended in semi-flu
31、id stromalChlorophylllGreen photosynthetic pigmentlChlorophyll capture solar energy47Energy-Related Organelles:ChloroplastslServe as the site of photosynthesis lCaptures light energy to drive cellular machinerylPhotosynthesislSynthesizes carbohydrates from CO2&H2OlMakes own food using CO2 as only ca
32、rbon sourcelInorganic molecules(Energy-poor compounds)are converted to organic molecules(energy-rich compounds)lOnly plants,algae,and certain bacteria are capable of conducting photosynthesis 48Chloroplast Structure49Energy-Related Organelles:MitochondrialSmaller than chloroplastlContain ribosomes a
33、nd their own DNA lSurrounded by a double membrane lInner membrane surrounds the matrix and is convoluted(folds)to form cristae.lMatrix Inner semifluid containing respiratory enzymeslBreak down carbohydrates lInvolved in cellular respirationlProduce most of ATP utilized by the celllContain their own
34、DNA and ribosome i.e.they are semiautonomouslInherited from Oocyte50Mitochondrial StructureMitochondrial Origin Hypothesis5152The CytoskeletonlMaintains cell shapelAssists in movement of cell and organelleslAids movement of materials in and out of cellslThree types of macromolecular fiberslMicrofila
35、mentlIntermediate FilamentslMicrotubuleslAssemble and disassemble as needed53The Cytoskeleton:Actin FilamentslMicrofilament are rods of actinlExtremely thin filaments like twisted pearl necklacelSupport for microvilli in intestinal cellslIntracellular traffic controllFor moving stuff around within c
36、elllCytoplasmic streaminglFunction in pseudopods of amoeboid cellslImportant component in muscle contraction54The Cytoskeleton:Actin Filament Operation55The Cytoskeleton:Intermediate FilamentslIntermediate in size between actin filaments and microtubuleslRope-like assembly of fibrous polypeptideslFu
37、nctions:lSupport nuclear envelopelCell-cell junctions,like those holding skin cells tightly together56The Cytoskeleton:MicrotubuleslHollow cylinders made of two globular proteins called a and b tubulinlSpontaneous pairing of a and b tubulin molecules form structures called dimerslDimers then arrange
38、 themselves into tubular spirals of 13 dimers aroundlAssembly:lUnder control of Microtubule Organizing Center(MTOC)lMost important MTOC is centrosomelFunction:lProvide framework for movement of organelle within celllDirect separation of chromosomes during cell division(e.g.Centrioles are composed of
39、 microtubules)lProvide locomotion and movement(e.g.flagella and cilia)57The Cytoskeleton:Microtubule Operation58The Cytoskeleton59Microtubular Arrays:CentrioleslShort,hollow cylinderslOne pair per animal celllLocated in centrosome of animal cellslOriented at right angles to each otherlSeparate durin
40、g mitosis to determine plane of division60Cytoskeleton:Centrioles61Microtubular Arrays:Cilia and FlagellalHair-like projections from cell surface that aid in cell movementlIn eukaryotes,cilia are much shorter than flagellalCilia move in coordinated waves like oarslFlagella move like a propeller or c
41、ork screw62Structure of a Flagellum63Comparison of Prokaryotic and Eukaryotic CellsMCAT Exam PrepPowerPoint Lecture Slides are prepared by Dr.Isaac Barjis,Biology Instructor64Membrane Structure and Function Lecture 165OutlinelMembrane ModelslFluid-MosaiclPlasma Membrane Structure and FunctionlPhosph
42、olipidslProteinslPlasma Membrane PermeabilitylDiffusionlOsmosislTransport Via Carrier ProteinslCell Surface Modifications66Structure and Function:The Phospholipid BilayerlThe plasma membrane is common to all cellslSeparates:lInternal living cytoplasmic fromlExternal environment of celllPhospholipid
43、bilayer:lExternal surface lined with hydrophilic polar headslCytoplasmic surface lined with hydrophilic polar headslNonpolar,hydrophobic,fatty-acid tails sandwiched in between67Unit Membrane68Membrane ModelslFluid-Mosaic ModellThree components:lBasic membrane referred to as phospholipid bilayerlProt
44、ein moleculeslFloat around like icebergs on a sealMembrane proteins may be peripheral or integrallPeripheral proteins are found on the inner membrane surfacelIntegral proteins are partially or wholly embedded(transmembrane)in the membranelSome have carbohydrate chains attachedlCholesterol69The Fluid
45、 Mosaic Model70Transmembrane Proteins71Functions of Membrane ProteinslChannel Proteins:lTubularlAllow passage of molecules through membranelCarrier Proteins:lCombine with substance to be transportedlAssist passage of molecules through membranelCell Recognition Proteins:lProvides unique chemical ID f
46、or cellslHelp body recognize foreign substanceslReceptor Proteins:lBinds with messenger moleculelCauses cell to respond to messagelEnzymatic Proteins:lCarry out metabolic reactions directly72Membrane Protein Diversity73Science Focus:Cell Signaling74Types of Transport:Active vs.PassivelPlasma membran
47、e is differentially(selectively)permeable lAllows some material to passlInhibits passage of other materialslPassive Transport:lNo ATP requirementlMolecules follow concentration gradientlActive TransportlRequires carrier proteinlRequires energy in form of ATP75Passage of Molecules Across the Membrane
48、76Types of Membrane Transport:Overview77Types of Transport:DiffusionlA solution consists of:lA solvent(liquid),andlA solute(dissolved solid)lDiffusionlNet movement of solute molecules down a concentration gradientlMolecules move both ways along gradientlMolecules move from high to lowl Equilibrium:l
49、When NET change stopslSolute concentration uniform no gradient78Gas Exchange in Lungs:Diffusion Across Lung79Types of Transport:OsmosislOsmosis:lSpecial case of diffusionlFocuses on solvent(water)movement rather than solutelDiffusion of water across a differentially(selectively)permeable membranelSo
50、lute concentration on one side high,but water concentration lowlSolute concentration on other side low,but water concentration highlWater diffuses both ways across membrane but solute cantlNet movement of water is toward low water(high solute)concentrationlOsmotic pressure is the pressure that devel
