Nucleic Acids and Proteins - Rochester City · PDF filethousands of genetic disorders ... of a...

1

macromolecules

proteins

composed of monomers

DNA

RNA

Unit xx, Lesson xxUnit xx, Lesson xx

Essential Questions• Whatisamonomer,andwhatrelationdoesithavetothestructureand

functionofpolymers?

• HowdonucleicacidmonomersinfluencethefunctionofDNAandRNA?

• Howdoesthesequenceofanaminoaciddeterminethethree-dimensionalstructureoftheprotein?

• Whatdoesdirectionalitymeanwhenreferringtonucleicacidsandproteins?

Unit 7, Lesson 1

Nucleic Acids and Proteins

Keywordsamino acid

dehydration synthesis

fatty acids

monomer

monosaccharides

non-polar molecule

nucleotide

nucleic acid

peptide bond

polar molecule

polymer

protein

rRNA

Copyright © 2011, K12 Inc. All rights reserved. This material may not be reproduced in whole or in part, including illustrations, without the express prior written consent of K12 Inc.

Unit 7, Lesson 1 Nucleic Acids and Proteins 2

Set the StageXXX

Set the StageAlthough one missing amino acid in a polypeptide or the wrong nucleotide in a nucleic acid sequence are small differences, they can have serious consequences for an organism. The wrong nucleotide in DNA or RNA can result in the wrong codon being used during the translation process and then the wrong amino acid being inserted into the final sequence. When the primary sequence of a protein is wrong, the protein will not fold in the same way it would have, and ultimately the function of the protein will be different or nonexistent. This can cause serious problems in a biological system that is dependent on thousands of pieces working harmoniously together for the wellbeing of the organism. If one part does not work, others might not either, the way a car would not work without a steering wheel.

An example of a problem that missing amino acids or wrong nucleotides can cause in humans is the disease of sickle-cell anemia, a genetic blood disorder that produces abnormal red blood cells with a tendency to form unwanted clots in the blood stream due to their sickle shape. This disease is the result of one monomer, glutamic acid, being substituted for the amino acid valine in the primary sequence of hemoglobin. It is only one example of the thousands of genetic disorders that can occur when one monomer is out of place.

Macromolecules are polymers made of connected monomers.Alllivingthingsareconstructedprimarilyfromfourmajormacromolecules:nucleicacids,proteins,lipids,andcarbohydrates.Nucleic acidisimportantinstoring,transmitting,andmakingusefultheinformationnecessaryfortheprocessesoflife.Proteiniscomposedofaminoacidsthatareimportantforlifefunctions.Lipidsarecomposedoffats,oils,phospholipids,steroids,andwaxes.Carbohydratesarelargeorganicmoleculesmadefromcarbon,oxygen,andhydrogen.

Figure 1. Sickle-shaped red blood cells are the result of a single base-change mutation.

nucleic acid a macro-molecule important in storing, transmitting, and making useful the information necessary for the processes of life

protein a macromole-cule composed of amino acids that are important for life functions



Themoleculesnucleicacids,proteins,lipids,andcarbohydratesarereferredtoas“macro”becauseofthelargenumberofatomsusedintheirconstructionandbecauseoftheirlargemolecularweight(oftenover100,000daltons).Themajor-ityofmacromoleculesarepolymers(PAH-luh-muhr),largemoleculesofrepeat-inggroupsofmolecularlyidentical,nearlyidentical,orcloselyrelatedsubunits.Thesepolymersubunitsareknownasmonomers(MAH-nuh-muhr).Withinanyparticularcell,thousandsofdifferentmacromoleculescanbefoundcarryingoutmanyimportantfunctions—allcontributingtotheprocessoflife.

Monomers are important to polymer structure and function. Eachclassofmacromoleculeismadeupofdifferenttypesofmonomers.Nucleicacidmonomersarecallednucleotides;proteinmonomersarecalledamino acids;lipidmonomersarecalledfatty acids;andcarbohydratemonomersarecalledmonosaccharides(MAH-nuh-SA-kuh-riyd).Alltypesofmonomersareorganicmolecules,meaningthattheycontaincarbon-to-carbonbonds.Com-monlythemonomerswillhavemanycarbonatomsbondedtogetherrepeatedlytoformchains,resemblingthestructureoffattyacids.Thesechainsarereferredtoascarbon“backbones”becauseoftheirrepetitiveappearance.Othertimesthecarbonatomsmaytaketheformofrings,astheydoinmonosaccharidesandnucleotides.

In addition to the numerous carbon atoms and bonds in thesemolecules, monomers may contain arrangements of atoms and bonds,called functional groups, which influence the function of the polymersinuniqueways.A common functional group found in amino acids is theamino group −NH2 (Figure 2). Other commonly occurring functionalgroups include carboxyl groups (−COOH) in amino acids, methyl groups(−CH3),andphosphategroups(–PO3)innucleicacids.Thevaryingchemicalpropertiesofthesefunctionalgroups,accordingtohowtheyareattachedtothevariouscarbonringsandchains,arethereasonthatdifferentmonomershaveuniquecharacteristics.

nucleotide a subunit of a nucleic acid that consists of a phosphate group, a five-carbon sugar, and a nitrog-enous base

amino acid the organ-ic molecules from which proteins are made

fatty acids the organic molecules that serve as the units from which lipids are made

monosaccharides the organic molecules from which carbohydrates are made

Figure 2. Functional groups are groups of atoms that attach to carbon backbones. Each group has different chemical properties that influence chemical interactions. These six functional groups are commonly found in biological chemicals.

O H hydroxyl group

O

Ccarbonyl group

O

C O Hcarboxyl group

H N

Hamino group

S H sulfhydryl group

O

O P OH

OHphosphate group

polymer large molecules of repeating groups of molecularly identical subunits

monomer building block molecules for polymers



Ultimately,thestructuresofthemonomersdeterminethecharacteristicsandfunctionofpolymersandtheorganismasawhole.Thestructureaffectstheorder,orientation,andenvironmentalinteractionofthelargermacromolecule.Themac-romoleculepropertiesthatariseduetothesemonomercharacteristicsarecalledemergentproperties.

Sincemonomerbuildingblocksconstitutethestructuresofalllifeonearth,andsincestructuredirectlyinfluencesthefunctionoforganisms,thislessonwilldevotesignificanttimetotheseimportantmoleculesandthemacromoleculestheyconstruct.

Connecting and disconnecting monomers occurs through condensation and hydrolysis reactions.Animportantpartofbiologyisknowingwhatpiecesmakeupmacromolecules.Howtheyareputtogetherandtakenapartisalsoimportantbecausemacromol-eculesarefrequentlyconstructedanddeconstructedwithmajorimplicationsforthefunctionoforganisms.Whenyoudigestfood,forexample,thecellsliningyourdigestivetractabsorbmonomersofthelipids,carbohydrates,andproteinsyoujustateandusethemasbuildingblockstoconstructtheirownmacromolecules.Thisutilizationispossiblebecauseoftwoopposingchemicalreactionsthatutilizemonomers,water,andenzymes.

Areactioncalleddehydration synthesis,orcondensation,connectstwomonomers.Thisprocessoccurswhenanenzymeremovesan−OHgroupfromtheendofonemonomerandan−Hatomfromanothermonomer.The−OHand−Hjointogether,creatingwater,whilethetwomonomersbecomeconnectedthroughacovalentbond(Figure 3).Thisprocessrequiresaninputofenergyfromthecelltobeaccomplished.Hydrolysis(watersplitting)breaksmonomersapartbydoingtheexactopposite.H2Oisattachedtoanenzymeandisbrokenwhenan−Hatomisconnectedtoonemonomerwhilethe−OHbecomesconnectedtotheother,breakingthecovalentbondthatholdsthemonomerstogether.

dehydration synthesis an enzymatic reaction that connects two monomers while creating a water molecule

Figure 3. A dehydration synthesis reaction occurs when an –OH group is removed from one chemical and an –H is removed from another. The two chemicals are bound together with a covalent bond, and a molecule of H2O is produced.

H N

H

C C OH

H2O

R

H O

H N

H

C C OH

R

H O

H N

H

C C

R

H O

N

H

C C OH

R

H O

+

+



DNA and RNA are important macromolecules. Thedouble-helixmacromoleculeDNAcontainsthegeneticinformationnecessarytoguideconstructionofalltheproteinsinacellandthusallowthecontinuityoflife.Asdiscussedpreviously,DNA’ssingle-strandedcounterpart,RNA,comesinthreeforms,eachwithaspecificfunctionthataidsproteinsynthesis.MessengerRNA(mRNA)transportstheinformationfromDNAtotheribosomes.Attheribosomes,tRNAtransfersthegeneticinformationintoasequenceofproteins,andrRNAservesasthebuildingblockofribosomes.ThesevariousDNAandRNApolymersaregenerallyreferredtoaspolynucleotides.

The structure of DNA and RNA determines their function. ThenucleicacidsDNAandRNAhavemanychemicalandstructuralsimilaritiesbutcanfunctiondifferentlybasedonthenucleotidemonomersfromwhichtheyareconstructed.DNAmonomersarecalledDNAnucleotides,andRNAmonomersarecalledRNAnucleotides.Bothtypesofnucleotidescontainafive-carbonsugarring,aphosphategroup,andanitrogen-containingbase(Figure 4).Thenitrogen-containingbaseconnectstothefirstcarbonofthesugarring,andthephosphateattachestothefifthcarbonofthesugarring.Thesenucleotidemonomerslinktogetherbyformingcovalentbonds,whichformarepeatingsugar-phosphateback-bonewiththesugarringofonenucleotideattachedtothephosphateofthenext.

TherearesomesubtlebutimportantdifferencesbetweenthestructuresofDNAandRNA(Figure 5).Onedifferenceisinthefive-carbonsugarrings.ThesugarinDNAnucleotides,deoxyribose,lacksanextra−OHfunctionalgroupthatthesugarinRNA,ribose,contains.ThisextrafunctionalgrouppreventsRNAfromformingthestabledouble-helixstructureofDNA.

Figure 4. A DNA nucleotide is made of a five-carbon sugar ring, a phosphate group, and a nitrogen base. Nucleotides are joined together where the phosphate group binds to the fifth carbon of the sugar ring.

Figure 5. RNA and DNA are both nucleic acids made of nucleotides. RNA is a single strand, and DNA is a double strand. RNA contains uracil instead of thymine, which is found in DNA.

S

P

P

SP

TA

S

P

P

S

CG

S

P

P

S

AT

S

P

P

S

TA

S

P

S

GCU

uracil

sugar-phosphate backbone

base pair

nucleotide

Tthymine

Aadenine

Aadenine

Gguanine

Gguanine

Ccytosine

Ccytosine

tRNA transfer RNA: a type of RNA molecule that carries amino acids to the site of protein synthesis in ribosomes

rRNA ribosomal RNA: a type of RNA molecule that makes up the main part of the structure of a ribosome



Thenitrogen-containingbasesarealsoslightlydifferentinDNAandRNA.DNAcontainscytosine,guanine,adenine,andthymine.InRNA,thebasethy-mineisreplacedwithuracil.Thesebasespairwitheachothertoformtherungsofthestepladderwithinthedoublehelix.Cytosineandguaninearecapableofpairingwitheachotherwhileadenineandthyminepairwitheachother.InRNA,adeninepairswithuracil.ThevariationinthesequenceofthesebasesisthecodeforthegeneticinformationthatDNAcontains.Basedonthedifferentmonomertypesthatareusedtoconstructthem,DNAandRNAarecapableofperformingverydifferentfunctions.

Proteins are macromolecules that have many functions in the cell. Proteinsplayasignificantroleinbiology:proteinmakesupover50%ofthemassofthetypicalcell,notcountingwater.Proteinscarryoutmanyfunctionswithincellsincludingstructuralsupport,moleculartransportation,andcell-to-cellcom-munication.Chemicalprocessesareacceleratedbyspecializedproteinscalledenzymes,whicharefoundabundantlyinlivingsystems.Althoughthousandsofproteinshavealreadybeendiscoveredandanalyzed,manyscientists,aidedbycontinualadvancesintechnology,continuetoinvestigatetheremainingundescribedproteins.

Amino acid monomers form proteins and determine protein function. Proteinmacromoleculesconsistofassortedaminoacidmonomersthatbecomelinkedtogetherviadehydrationsynthesis(Figure 6)likebeadsonanecklace.Atypicalproteinmightcontainabout100linkedmonomers.Yetallproteinsareconstructedfromonly20differentaminoacids.AswithDNAnucleotides,theorderinwhichthepiecesareputtogetherisnearlylimitless.Formingdifferentproteinsusingonly20aminoacidsiscomparabletoformingmanywordsinalanguageusingonly26lettersinthealphabet.Similartotheorderinnucleotides,theorderinwhichtheseindividualaminoacidmonomersarejoinedultimatelydeterminesthefunctionandpropertiesofeachprotein.

H

H

C C

O

OHR

N

Amino Group Carboxyl Group

H

Figure 6. An amino acid consists of an amino group, a hydrogen atom, a carboxyl group, and the variable R group.

1SeLF-CheCK

How are monomers

capable of interacting in

such a way that allows

dehydration synthesis or

hydrolysis reactions

to occur?


Unit 7, Lesson 1 Nucleic Acids and Proteins 7Unit 7, Lesson 1 Nucleic Acids and Proteins

Figure 7. R groups attach to the central atom of an amino acid molecule. The bond location on each R group is represented by a single-sided bond.

AMINO ACIDS AND THEIR R-GROUPS

Amino Acid R-Group Amino Acid R-Group

GlycineH

Threonine CHCH3HO

AlanineCH3

Cysteine H2C

SH

Proline* H

N

H2C C C

H2C CH2 OH

OAsparagine

CH2

NH2

CO

ValineCH

H3C CH3

Glutamine CH2

C

H2C

OH2N

Isoleucine

C H2

CHH3CCH3

SerineH2C

OH

Leucine

CH

H3C CH2

CH3

Aspartic acidCH2

OH

CO

Methionine

H2C

H3C

CH2

S

Glutamic acid CH2

C

H2C

OHO

Tryptophan

HC

C HC

HC

C

C

CH

NH

CH2

CH

Lysine

CH2H2CH2N

CH2CH2

Phenylalanine

HO

HC

C C

HC

CH

CH2

CH

Arginine CH2

HNH2C

C N H

CH2

H2N

Tyrosine

HOC

C HC

HC

CH

CH2

CH

Histidine

HC

C CH2

NH

N

HC

*Because the R group binds to the NH2 as well as to the stem, the entire amino acid is shown instead of just the R group.



Aminoacidsarecomposedofacentralcarbonatomconnectedonfoursidesbyacarboxylgroup,anaminogroup,ahydrogenatom,andavariablegroupreferredtoastheRgroup.ItistheRgroupthatdiffersfromaminoacidtoaminoacid,makingeachonechemicallyuniqueandprovidingeachonewithspecificchemicalproperties.

Whentwoaminoacidsarejoinedtogetherduringadehydrationreaction,theyformapeptide bondwhereintheaminogroupfromoneaminoacidjoinswiththecarboxylgroupoftheotheraminoacid(Figure 7).Aspecialenzymehelpsformapeptidebondbyfacilitatingthedehydrationsynthesisprocessthatremovesawatermoleculeandconnectsthemonomerstogether.

Protein monomers interact chemically with one another. AminoacidscanbeclassifiedbasedonthetypeofRgrouptheypossess.Non-polarRgroupsarecomposedofachemicalstructurethatrepelspolarmoleculessuchaswater.PolarRgroupsdojusttheopposite,chemicallyattractingotherpolargroups,includingwater.Whenthepolarandnon-polarRgroupsofdifferentaminoacidsinteractwitheachother,theresultmaybeahydrophobicorhydrophilicinteraction.Inhydrophobicinteractions,thenon-polargroupsinteractbyclusteringtogetherontheinsideoftheproteinawayfromthewaterontheoutside.InhydrophilicinteractionsthepolarRgroupsinteractsothattheyfaceoutwardswheretheyareexposedtowater.Ahelpfulwaytorememberthisistoknowthathydrophobicmeans“waterfearing,”sothesemoleculesareinsolubleinwater,andhydrophilicmeans“waterloving,”sothesemoleculesaresolubleinwater.Theseinteractionsoccurprimarilybecausepolarmoleculescanhydrogenbondwitheachotherbuttheycannothydrogenbondwithnon-polarmolecules.

Inadditiontohydrophobicandhydrophilicinteractions,aminoacidscaninteractinotherways.Ionicbondscanformbetweenchargedatoms(anionsandcations)indifferentmolecules.APolarbondisatypeofcovalentbondthatdoesnotsharetheelectronsequallybetweenthetwoatomsbecauseoneismoreelec-tronegativethantheother.VanderWaalsinteractionsoccurwhenpositiveandnegativechargedareasofmoleculesgetclosetoeachotheruntiltheyweaklysticktooneanother.WhentwoRgroupscontainingsulfhydrylgroups(−SH)approacheachotherinafoldedprotein(thesearefoundoncysteinemonomers),theywillformadisulfidebridgewiththetwosulfuratomsformingabond.

Proteins can obtain four different configurations depending on how the monomers interact chemically with one another. Aproteincontainsnumerousaminoacidsheldtogetherbypeptidebondsinauniquesequenceknownasitsprimarystructure(Figure 8).Theprimarystructurecanbecomefolded,however,ashydrogenbondsformbetweenthecarbonandnitrogenelementsofthepolypeptidebackbone,formingwhatisknownasthesecondarystructureoftheprotein.Thissecondarystructuremaytaketheconformationofeitheranαhelix(alphahelix),acoiledorspiralshape,oraβpleated(betapleated)sheet,resemblingrowsofmonomersfoldedbackoneachother.

2SeLF-CheCK

How do DNA

nucleotides and RNA

nucleotides differ from

one another?

non-polar molecule a molecule that lacks a dipole or permanent positive and negative areas

polar molecule a molecule in which there are positive and negative areas

peptide bond a chemical bond connect-ing two amino acids with the carboxyl group of one and the amino group of the other



Allofthepreviouslydescribedchemical-bondinginteractionsoccurbetweentheRgroupsofthevariousaminoacidsinaproteinandtheenvironmentwheretheinteractionoccurs.Thus,proteinscanspontaneouslyarrangethemselvesintoauniquethree-dimensionalconfigurationcalledthetertiarystructure.Althoughthebondsthatformtocreatethesethree-dimensionalconfigurationsareweak,theycanstabilizethestructureenoughsothatitremainsfolded.

Morethanonepolypeptidechaininafunctioningproteincauseinteractionsthatformthequaternarystructure.Mostfunctionalproteinsexistinthisform.SimilarchemicalinteractionsinvolvingtheRgroupsandtheenvironmentoccurinboththequaternarystructureandthetertiarystructure.

A protein’s environment interacts chemically with protein monomers and can affect protein structure. Justasproteinmonomerscaninteractwitheachotherchemically,resultinginchangesofconformation,theycanalsointeractwithmoleculesintheirsurroundingenviron-ment.Infact,itispossibletochangetheenvironmentofaproteintochangethestructureofaprotein.AlteringthepH,saltconcentration,ortemperatureoftheenvi-ronmentcanresultindenaturation,achangeofconformationthatcausesfunctionlossthatmayormaynotbereversible.Whenaneggisplacedinahotfryingpan,theheatcausesdenaturationoftheproteins,resultinginacookedegg.Becausethisdenaturationdisturbstheprimarystructureoftheprotein,itisnotpossiblefortheproteinsinacookedeggtorevertbacktotheiruncookedform.However,iftheprimarystructureisundisturbed,itispossibletoreturnaproteintoitsfunctionalshape.Thisiscommonlydoneinthelaboratorybyremovingthedenaturingagentfromatest-tubesolution.Forexample,thepHcanbechangedbacktowhatitwasoriginally,allowingtheproteinmonomerstoreformtheirchemicalbondswitheachotherandtore-fold.

The unique shape of each protein results in a unique function.Thefunctionofeachproteinisdeterminedbyitsstructure.Itisthroughtheprimarystructureofaproteinthatthefinaltertiaryorquaternarystructuretakesshapeandbecomesafunctionalprotein.Thefinalshapeofaproteinallowsittointeractwithotherproteinsandmoleculesasrequiredincellprocesses,muchasakeyandalockinteract.Oneproteinwillfunctioninacertaincapacityandincurparticularresultsthatanother

Figure 8. Proteins are made of amino acids connected by peptide bonds. These polypeptide chains can fold to form the complex three-dimensional structure of a protein.

peptide bonds amino acids

tertiary structure quaternary structureprimary structure secondary structure



proteinisnotabletoincur,facilitatedbyitsstructure.Thoughthisconceptmayseemstraightforwardinatextbook,forscientiststryingtomakesenseofthethousandsofproteinsinteractingwithmoleculesincellsthroughoutanorganism,discoveringhowtheseinteractionsoccurinreallifeisanintense,ongoing,andoftenpuzzlingtask.

Macromolecules have directionality. Nucleicacidsandproteinsshareacharacteristic,directionality,whichaffectshowothermoleculesinteractwiththem.Directionalityexistswheneachendofthemoleculeisdifferentfromtheother.Thischaracteristicofsomemacromoleculescanaffecthowtheyfunctionandhowothermoleculesinteractwiththem.

The directionality of nucleic acids affects their function. InDNAandRNA,oneendhasasugarmoleculewhiletheotherhasaphosphatepart.Thesugarendandphosphateendhavespecificnamesderivedfromthecarbonnumbertheyareattachedto.Inthesugar-phosphatebackbone,theendwithaphosphategroupattachedtoitisknownasthe5’(fiveprime)end,whiletheonewiththesugarisknownasthe3’end(Figure 9).Thenitrogenousbasesbranchofffromanendwheretheymaypairwiththeircomplementarybasesonanothernucleicacidthatrunsantiparalleltothefirstnucleicacid—its5’to3’backboneisgoingintheoppositedirection,thesamewaythetrafficoneachsideofatwo-waystreetmovesinoppositedirections.Forexample,ifthesequenceononestrandofDNAwascoded5’AGTACto3’,itsantiparallelstrandthatcomprisesthecomplementaryhalfofthedouble-helixwouldread3’TCATGto5’.

hydrogen bonds

5’ 3’

3’ 5’

S

P

P

S

TA

S

P

P

S

CG

S

P

P

S

AT

S

P

P

S

TA

S

P

S

GC


nucleotide base pairs


P

3SeLF-CheCK

What environmental

factors might affect a

protein’s function?

Figure 9. DNA replication takes place in a 5’ to 3’ direction. The leading strand is constructed continuously while the lagging strand is constructed in short seg-ments known as Okazaki fragments. These fragments are then connected to form a continuous strand of DNA.



DuringDNAreplication,directionalityimpactshowthenewDNAstrandsareputtogether.Elongationmusttakeplaceina5’to3’direction.Therefore,theDNApolymerasemovingdownthe3’to5’parentalDNAstrandhasnoproblemfollow-ingtheruleforelongationdirectionalitywhenthenewleadingstrandofDNAisconstructed.Forthepolymeraseworkingonthe5’to3’parentalstrand,however,itisnecessarytoconstructthisnewlaggingstrandofDNAinshortsegmentsbetween1,000and2,000nucleotideslong.TheseshortsegmentsofunconnectedDNAareknownasOkazakifragmentsuntiltheyareeffectuallystitchedtogetherbytheenzymeDNAligase.Duringthetranscriptionprocess,RNAiscompiledfromits5’endtoits3’end.TheRNApolymerasemovesdownstreamalongtheDNAgeneitistranscribingina3’to5’direction.DirectionalityalsoaffectsthefunctionofRNAduringthetranslationprocess.Theribosomeattachestothe5’endofmRNAasguidedbythepresenceofa5’capandpoly(A)tailonthe3’end.Becauseofthisattachment,tRNAcanassemblethecorrectproteinsequencesusingthethreenucleotide-widecodons.

The directionality of proteins affects their function.Proteinsalsoutilizedirectionality:oneendisalwaysacarboxylgroupwhiletheotherisanaminogroup.Thereareenzymesinourbodiesthatonlyworkononeendortheotherofapolypeptide.Thisisthecasewithsomediges-tiveenzymes.

4SeLF-CheCK

What are some

implications of

directionality in DNA

and RNA function?

Extensions • Locateandreadafewcurrenteventarticlesorwatchafewvideosabout

geneticengineering.Howmightadvancesinthefieldofgeneticengineeringaffectyounowandinthefuture?

• Findouthowgenetictestingisconducted.Whataresomeethicalprosandconstousingthistechnology?

• Exploregeneticdiseases.Whataresomeexplanationsforwhytherearesomanydifferentgeneticdiseases?

SummaryMacromoleculesarethebuildingblocksofalllivingthings.Similarly,monomersarethebuildingblocksofmacromolecules.Polymersareconstructedanddestructedthroughchemicalreactionsutilizingenzymes,water,andmonomers.DNAandRNAnucleotidesjointoformthe“backbone”and“stepladder”featuresofDNAandRNA.Functionalgroupsareimportantaspectsofmonomerstructurethatal-lowfordifferentchemicalbondstoformbetweenmolecules.Proteinsinparticularareaffectedbychemicalbondingbecausethesebondscausethemtoreshapeintosecondary,tertiary,andquaternarystructures.Environmentalvariablescaninterferewiththesechemicalbondsandcauseproteinstodenature.Somemacromolecules,includingDNA,RNA,andproteins,areaffectedbydirectionality,whichalsoimpactshowtheyareabletofunction.



1. Monomers can interact in dehydration synthesis and hydration reactions because enzymes facilitate these interactions.

2. Compared to DNA, the sugar in RNA contains an extra –OH functional group, and the base thymine is replaced with uracil in RNA nucleotides.

3. Temperature, pH, and salt concentration are three factors that may interfere with protein function.

4. Because of directionality, a leading strand and a lagging strand are necessary during DNA replication, and special tags are necessary during translation to guide the ribosome to the correct binding location.

SeLF-CheCK ANSweRS

ConnectionsSinceallittakestowreakhavocinanorderlybiologicalsystemistoreplaceonemonomerforanotherinaprotein’sprimarysequence,itseemssystemswouldbedisorderedmoreoften.ButonlyoneintenbillionDNAnucleotidesgetsthroughthesystemtocauseproblems.Howisitpossible,whenthousandsofproteinsareproducedinthehumanbody,forthingsnottogowrongmoreoften?Theanswerliespartiallyinabuilt-insafetycheckthatoccursduringtheDNAreplicationpro-cessitself.DNApolymerase,thesameenzymethatputsnucleotidebasesinplacetobeginwith,double-checksitsworkasitgoes.Anymistakethatgetsthroughthisprocesshasasecondchancetobecorrectedthroughmismatchrepair,aprocessthatinvolvesaspecialenzymetofixwronglyplacednucleotidesinacompletedsequence.Thankstothesetwoprocesses,thechanceofsomethinggoingwrongduringproteinsynthesisisgreatlyreduced,whilethechancesofproducingafullyfunctionalorganismareincreasedsubstantially.


Unit 7 Lesson 1All images © K12 Inc. unless otherwise noted. 2 Normal red blood cell and a sickle cell. Dr. Stanley Flegler/Visuals Unlimited, Inc.


Nucleic Acids and Proteins - Rochester City · PDF filethousands of genetic disorders ... of a...

Documents

Transcript of Nucleic Acids and Proteins - Rochester City · PDF filethousands of genetic disorders ... of a...