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NIS - BIOLOGY

NIS - BIOLOGY. Lecture 21 Cell Discovery and Theory Ozgur Unal. Cell. Observe the cork given to you and try to describe what you see. Using the microscope , look at the cork and describe what you see. A cell is the basic structural and functional unit of all living things .

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NIS - BIOLOGY

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  1. NIS - BIOLOGY Lecture 21 CellDiscoveryandTheory OzgurUnal

  2. Cell • Observethecorkgiventoyouandtrytodescribewhatyousee. • Usingthemicroscope, look at thecorkanddescribewhatyousee. A cellis thebasicstructuralandfunctionalunit of alllivingthings. Cellsarethebuildingblocks of organisms. Howsmall do youthinkcellsare? How many cells do you think you have in your body?

  3. History of theCellTheory In 1590, HansandZachariasJansseninventedthefirstcompoundmicroscope. In 1655, Robert Hookeobservedcorkand namedthetinychambersthat he sawcells. In 1683, DutchbiologistAnton vanLeeuwenhoekdiscovered single-celledorganisms. In 1830-1855, scientists discoveredthatplantsand animalshavecellsandallcellsareproducedfromthedivision of existingcells. Figure 7.1

  4. CellTheory Allthesediscoveriesleadtothecelltheorywiththreeprinciples: Alllivingorganismsarecomposed of oneormorecells. Cellsarethebasicunit of structureandorganization of alllivingorganisms. Cellsariseonlyfrompreviouslyexistingcells, withcellspassingcopies of theirgeneticmaterial on totheirdaughtercells. • Howwerescientistsabletoobservecells inthepast? • What tools do theyusetostudycellstoday?

  5. MicroscopeTechnology Thediscovery of cellsandthedevelopment of thecelltheorywould not be possiblewithoutmicroscopes. Miscroscopeshelp us seeverysmallobjects. Therearetwoimportantcharacteristics of microscopes: Magnification Resolution • Highermagnificationhelpsyouseesmallerobjects. • Higherresolutionhelpsyouseetwoobjectsveryclosetoeachother (help us toseethedetails)

  6. MicroscopeTechnology • Compoundlightmicroscopes: • Consists of a series of lensesand • usesvisiblelight. • Contains an eyepieceand an • objective lens. • Maximummagnificationaround 1000x. • Electronmicroscopes: • Useelectronstoproducemagnifiedimages. • TransmissionElectronmicroscopes (TEM) magnifyupto 500,000x. • Scanningelectronmicroscopes (SEM) produce 3-D images. • TEM and SEM can be usedonlyfordeadcells.

  7. ElectronMicroscopes • ScanningTunnelingElectron • Microscopes (STM) can be used • forlivespecimens. • STMsproduce 3-D imagesfor • verysmallobjects.

  8. BasicCellTypes • Youhaveprobablyrealizedthatthecellsthatmakeuporganismsmusthavedifferenttypes. • Forexample, thecells in a plantaredifferentthantheones in a animal. • Scientisthavegroupedcellsintotwobroadcategory: • Prokaryoticcellsand Eukaryoticcells. Youseeimages of two differentcells. Listthe similaritiesanddifferences betweeneach.

  9. BasicCellTypes • Bothtypes of cellhave a boundary. • A plasmamembraneis a specialboundarythathelpscontrolwhatentersandleavesthecell. • Plasmamembraneexists • in allcells. • Allcellscontaingenetic • materialthatprovides • instructions.

  10. BasicCellTypes • EukaryoticCells: • Thesecells haveinternal structurescalledorganelles. • Eachorganellecarriesoutspecificcellfunctions. • Nucleus is a centralorganellethatcontainscell’sgeneticmaterial in the form of DNA. • Mostorganismsaremadeup • of eukaryoticcellsandare • calledeukaryotes. • Therearesomeunicellular • organismsthatareeukaryotes.

  11. BasicCellTypes • ProkaryoticCells: • Thesecellsaredefined as cellswithout a nucleusorothermembrane-boundorganelles. • Manyscientiststhinkthatprokaryotesaresimilartothefirstorgansism on Earth. • Upto 100 timessmaller • thaneukaryoticcells.

  12. Origin of CellDiversity • Whyaretheretwobasictypes of cells? • Eukaryoticcellsprobablyevolvedfromprokaryoticcellsmillions of yearsago. • Accordingtoendosymbionttheory, a symbioticmutualrelationshipinvolvedoneprokaryoticcellliving inside another. (Thiswill be discussed in Chapter 14) • Eukaryoticcellsarelargerandhavedistinctorganelles. • Thesecellshavedevelopedspecificfunctionsandthisleadtothecelldiversity, such as nervecells, bone cells, leafcells, stemcellsetc.

  13. NIS - BIOLOGY Lecture 22 PlasmaMembrane OzgurUnal

  14. Function of thePlasmaMembrane Look at thefilterpaper as I pourmuddywater on it. Answerthefollowingquestions. What did you just observe? What is the purpose of the filter here? What type of particlesare selected by the filter paperto pass? What type of particlesarenot selected by the filterpaper to pass?

  15. Function of thePlasmaMembrane Howaboutthisfishnet? What is thepurpose of thisfishnet?

  16. Function of thePlasmaMembrane • Rememberthatplasmamembraneis a specialboundarythathelpscontrolwhat • entersandleaves a cell. • Plasmamembrane is a • thinandandflexible • boundarybetween a cell • anditsenvironment. Do youthinkcellsneedsuch a filteringsystem? Whatcontrolswhatentersandleaves a cell?

  17. Function of thePlasmaMembrane Homeostasis is importantforcells. Plasmamembraneallowsnutrientsintothecellandallowswasteandotherproductsleavethecell. A keyproperty of theplasmamembrane is selectivepermeability. Byselectivepermeability, a membraneallowssomesubstancestopassthroughwhilekeepingothersout. Thestructure of plasmamembranecontrolshow, whenandhowmuch of thesesubstancesenterandleave a cell. http://education.uoit.ca/lordec/ID_LORDEC/diffusion_osmosis/garib_diffusion_osmosis.swf

  18. Structure of thePlasmaMembrane Most of themolecules in theplasmamembranearelipids. Plasmamembrane is composed of phospholipidbilayer, in whichtwolayers of phospholipidsarearrangedtailtotail. Figure 7.6 Phospholipidshave a polar headand a non-polar tail. What is theadvantage of havingnon-polar tails in a plasmamembrane?

  19. Structure of thePlasmaMembrane Plasmamembraneanimations: http://telstar.ote.cmu.edu/biology/downloads/membranes/ http://www.yellowtang.org/animations/bilayer.swf • Do youthink vitamin C can entercells? • No, although vitamin C is water-soluble it acnnotdiffusethroughtheplasmamembranebecause it is a charged, polar molecule.

  20. Structure of thePlasmaMembrane Movingwithandamongthephospholipids in theplasmamembranearecholesterol, proteinsandcarbohydrates. Proteins at theinnersurfaceanchortheplasmamembranetothecell’sinternalstructure, givingthecellitsshape. Transport proteinsmoveneededsubstancesorwastesthroughtheplasmamembrane, contributingtotheselective permeability.

  21. Structure of thePlasmaMembrane Nonpolarcholesterol is repelledbywaterand it is positionedamongphospholipids. Cholesterolpreventsphospholipidsbilayertailsfromstickingtogether. Thiscontributestothefluidity of theplasmamembrane. • Carbohydrates in themembraneareattachedtoproteinsadntheystickoutto define cell’scharacteristicsandhelpidentifychemicalsignals. • Forexample, carbohydrates in themembranehelpdiseasefightingcellsrecognizeandattackpotentiallyharmfulcells.

  22. Structure of thePlasmaMembrane Phospholipidsbilayer in theplasmamembranecreate a “sea” in whichothermolecules can float. Phospholipids can movesideways in themembrane. Components of theplasmamembraneare in constantmotion, slidingpasteachother. Fluid-mosaic model of theplasmamembraneexplainsthischaracteristics. http://telstar.ote.cmu.edu/biology/downloads/membranes/

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