summary.docx
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summary.docx
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summary
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1.Activitiesoflivingorganismsoriginateincells.Structureandgrowthareamongtheattributesoflivingorganisms.Growthhasbeendescribedasanincreaseinvolume;itresultsprimarilyfromtheproductionofnewcells.Variationsinformmaybeinheritedorresultfromresponsetotheenvironment.
2.Reproductioninvolvesoffspringthatarealwayssimilarinformtotheirparents;ifreproductionceases,theorganismbecomesextinct.Plantsgenerallyrespondtostimulimoreslowlyandinadifferentfashionfromanimals.
3.Alllivingorganismsexhibitmetabolicactivities,includingrespiration,digestion,assimilation,productionofnewcytoplasm,and,ingreenorganisms,photosynthesis;theyalsoallexhibitmovement.Cyclosisisthestreamingmotionofcytoplasmwithinlivingcells.Livingorganismshaveamuchmorecomplexstructurethannonlivingobjectsandareadaptedtotheirindividualenvironments.
4.Thebasic"stuffoftheuniverse"iscalledmatter,whichoccursinsolid,liquid,orgaseousform.Itiscomposedofelements,ofwhichthesmalleststablesubdivisionisanatom.Atomicnucleicontainpositivelychargedprotonsandunchargedneutrons;thenucleiaresurroundedbymuchlargerorbitalsofwhirling,negativelychargedelectrons.Isotopesareformsofelementsthathaveslightvariationsinthenumberofneutronsintheiratoms.
5.Thecombiningcapacitiesofatomsorionsarecalledvalence.Atomscanbondtootheratoms,andthoseofmostelementsdonotexistindependently;compoundsaresubstancescomposedoftwoormoreelementscombinedinadefiniteratiobychemicalbonds;moleculesarethesmallestindependentlyexistingparticles.Inacovalentbond,pairsofelectronslinktwoormoreatomicnuclei;nitrogenand/oroxygenatomsofonemoleculemayformweakhydrogenbondswithhydrogenatomsofothermolecules.Ifamoleculelosesorgainselectrons,itbecomesanion,whichmayformanionicbondwithanotherion.
6.Watermoleculesarepolarbecausetheyareasymmetricalinshape.Watermoleculescoheretoeachotherandadheretoothermolecules.
7.Acidsreleasepositivelychargedhydrogenionswhendissolvedinwater.Basesreleasenegativelychargedhydroxylionswhendissolvedinwater.ThepHscaleisusedtomeasuredegreesofacidityoralkalinity.Saltsandwaterareformedwhenacidsandbasesaremixed.
8.Energycanbedefinedas"abilitytoproduceachangeinmotionormatter"oras"abilitytodowork."Itsformsincludechemical,electrical,heat,light,kinetic,andpotential.Thefartherawayfromthenucleusanelectronis,thegreatertheamountofenergyrequiredtokeepitthere.
9.Cellsarecomposedofcarbon,hydrogen,oxygen,andnitrogen,withalittlephosphorusandpotassium,plussmallamountsofotherelements.Aplantmayconvertthesimplemoleculesorionsitrecyclesorabsorbsfromthesoiltoverylarge,complexmolecules.Organicmoleculesareusuallylargepolymersthathavea"backbone"ofcarbonatoms.
10.Carbohydratescontaincarbon,hydrogen,andoxygeninaratioof1C:
2H:
1O.Carbohydratesoccurasmonosaccharides(simplesugars)anddisaccharides(twosimplesugarsjoinedtogether).Polysaccharidesmayconsistofmanysimplesugarscondensedtogether;othersaremorecomplex.Simplesugars,whentheyareattachedtooneanother,eachgiveupamoleculeofwater,formingstarch.Hydrolysisinvolvesrestoringawatermoleculetoeachsimplesugarwhenstarchisbrokendownduringdigestion.
11.Lipids(e.g.,fats,oils,andwaxes),whichareinsolubleinwater,consistofaunitofglycerolorotheralcoholwiththreefattyacidsattached.Theycontaincarbon,hydrogen,andoxygen,withproportionatelymuchlessoxygenthanisfoundincarbohydrates.Saturatedfatshavehydrogenatomsattachedtoeveryavailableattachmentpointoftheircarbonatoms;ifthereareveryfewplacesforhydrogenatomstoattach,thefatissaidtobepolyunsaturated.Phospholipidshaveaphosphategroupreplacingonefattyacid.
12.Proteinsareusuallylargemoleculescomposedofsubunitscalledaminoacids.Eachaminoacidhasanaminogroup(-NH2)andacarboxylgroup(-COOH);thesegroupsbondaminoacidstogether,formingpolypeptidechains;thebondsarecalledpeptidebonds.Enzymesarelargeproteinmoleculesthatfunctionasorganiccatalysts.Theirnamesendin-ase.Somehaveimportantindustrialuses.
13.Therearetwonucleicacids(DNAandRNA)associatedprimarilywithcellnuclei.DNAandRNAmoleculesconsistofchainsofnucleotides.Fourkindsofnucleotides,eachwithauniquenitrogenousbase,occurinDNA.HelicalcoilsofDNAcontaincodedinformationdeterminingthenatureandproportionsofsubstancesincellsandtheultimateformandstructureoftheorganism.RNAhasadifferentsugarandnucleotide.
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1.Alllivingorganismsarecomposedofcells.Cellsaremodifiedaccordingtothefunctionstheyperform;someliveforafewdays,whileothersliveformanyyears.
2.Thediscoveryofcellsisassociatedwiththedevelopmentofthemicroscope.In1665,RobertHookecoinedthewordcellsforboxlikecompartmentshesawincork.LeeuwenhoekandGrewreportedfrequentlyduringthenext50yearsontheexistenceofcellsinavarietyoftissues.
3.In1809,Lamarckconcludedthatalllivingtissueiscomposedofcells,andin1824,DutrochetreinforcedLamarck'sconclusions.In1833,Browndiscoveredthatallcellscontainanucleus,andshortlythereafter,Schleidensawanucleoluswithinanucleus.SchleidenandSchwannarecreditedwithdevelopingthecelltheoryin1838to1839.Thetheoryholdsthatalllivingorganismsarecomposedofcellsandthatcellsformaunifyingstructuralbasisoforganization.
4.In1858,Virchowcontendedthateverycellcomesfromapreexistingcellandthatthereisnospontaneousgenerationofcellsfromdust.In1862,PasteurexperimentallyconfirmedVirchow'scontentionsandlaterprovedthatfermentationinvolvesactivityofyeastcells.In1897,Buchnerfoundthatyeastcellsdonotneedtobealiveforfermentationtooccur.Thisledtothediscoveryofenzymes.
5.Lightmicroscopescanmagnifyupto1,500times.Thinlyslicedmaterialscanbeviewedwithcompoundmicroscopes.Opaqueobjectscanbeviewedwithstereomicroscopes;mostmagnifyupto30times.
6.Electronmicroscopeshaveelectromagneticlensesandabeamofelectronswithinavacuumthatachievemagnification.Transmissionelectronmicroscopesmagnifyupto200,000ormoretimes.Scanningelectronmicroscopes,whichcanbeusedwithopaqueobjects,usuallymagnifyupto10,000times.
7.Scanningtunnelingmicroscopesuseaminuteprobetoscansurfacesatawidthasnarrowasthatoftwoatoms.
8.Eukaryoticcellsarethesubjectofthischapter.Prokaryoticcells,whichlacksomeofthefeaturesofeukaryoticcells,arediscussedinChapter17.
9.Cellsareminute,varyingindiameterbetween10and100micrometers.Theynumberintothebillionsinlargerorganisms,suchastrees.Plantcellsareboundedbywallsthatsurroundthelivingprotoplast.Thecytoplasmcontainsasouplikefluidcalledthecytosolandallcellularcomponentsbetweentheplasmamembraneandnucleus.
10.Apecticmiddlelamellaissandwichedbetweentheprimarycellwallsofadjacentcells.Theprimarywallandalsothesecondarycellwall,oftenaddedinsidetheprimarywall,arecomposedofcellulosepolymers,withhemicellulosesandglycoproteins.Secondarycellwallscontainligninthatstrengthensthewall.
11.Livingcellsareincontactwithoneanotherviafinestrandsofcytoplasmcalledplasmodesmata,whichoftenextendthroughminuteholesinthewalls.
12.Aflexibleplasmamembrane,whichissandwich-likeandoftenformsfolds,constitutestheouterboundaryofthecytoplasm.Itregulatesthesubstancesthatenterandleavethecell.
13.Thenucleusisboundedbyanuclearenvelopeconsistingoftwomembranesthatareperforatedbynumerouspores.Withinthenucleusareafluidcallednucleoplasm,oneormoresphericalnucleoli,andthinstrandsofchromatin,whichcondenseandbecomechromosomeswhennucleidivide.Eachspeciesoforganismhasaspecificnumberofchromosomesineachcell.
14.Theendoplasmicreticulumisasystemofflattenedsacsandtubesassociatedwiththestoringandtransportingofproteinandothercellproducts.Granularparticlescalledribosomes,whichfunctioninproteinsynthesis,maylinetheoutersurfacesoftheendoplasmicreticulum.Ribosomesalsooccurindependentlyinthecytoplasm.
15.Dictyosomesarestructuresthatappearasstacksofsacsandfunctionascollectingandpackagingcentersforthecell.
16.Plastidsarelargergreen,orange,red,orcolorlessorganelles.Greenplastids,knownaschloroplasts,containenzymesthatcatalyzereactionsofphotosynthesis.Thesereactionstakeplaceinthemembranesofstructuresthatresemblestacksofcoins,calledthylakoids,aswellasthesurroundingmatrix,calledthestroma.Plastidsdevelopfromproplastids,whichdividefrequently,andalsoarisefromthedivisionofmatureplastids.
17.Mitochondriaaretiny,numerousorganellesthatareboundedbytwomembraneswithinnerplatelikefoldscalledcristae;theyareassociatedwithcellularrespiration.
18.Oneormorevacuolesmayoccupy90%ormoreofthevolumeofamaturecell.Vacuolesareboundedbyavacuolarmembrane(tonoplast)andcontainawateryfluidcalledcellsap.Cellsapcontainsdissolvedsubstancesandsometimeswater-solubleredorblueanthocyaninpigments.
19.Thecytoskeleton,whichisinvolvedinthearchitectureofcellsandinternalmovement,iscomposedofmicrotubulesandmicrofilaments.Microfilamentsmayberesponsibleforcytoplasmicstreaming.
20.Cellsthatarenotdividingareininterphase,whichis
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