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Proteins are a class of ubiquitous macromolecules in

all organisms.The Importance is implied in the nameproteioswhichmeans"firstplaceinGreek.

Theyplayaroleinalmostallprocessesinthebodyincluding:

OxygentransportGeneRegulation

Celltocellrecognition

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TypeofProtein Function Examples

Transport Proteins Transportsubstancesacrossmembranes

Ionchannel,Atpasepumps

Storage Proteins Storageandreleaseofaminoacids

Seedproteinsbrokendownduringgermination

Enzymes Catalyst hydrolyzes

Structural Proteins Supportcellularstructures Collageninconnectivetissue:keratininhairandnails

Regulatory Proteins Regulatecellularfunctions Transcriptionfactorsthatbind

toDNAandregulateexpression

Motility Proteins Movementofthecell Actinandmyosininmuscles;tublininciliaandflagella

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TheMonomersareAminoAcidsProteins are made from a linear sequence of amino

acids.

There are 20 amino acids that are used in thesynthesis ofproteins.

Every amino acid has the same basicstructure.They carry and amino group, a hydrogenatom, and a side chain know as the R group. All are

attached to a central carbon atom know as thealpha carbon.

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ThemonomersareAminoAcids

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AminoAcidsThecentralcarbonisasymmetricinallaminoacids

exceptforglycinewhichhasahydrogenasanRgroupandthereforecanexistintwoisomericformscalledLandD-aminoacids.BothformsexistinnaturebutonlyL-aminoacidsoccurinproteinsynthesis.

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Zwi2erions

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AminoAcidsAll20aminoacidshavecommonstructurebutdifferin

theirRgroup.Therefore,thechemicalnatureoftheaminoacidscomefortheRgroup.

9ofthisaminoacidshavenonpolarRgroupsandarethereforehydrophobic.Theseareusuallyfoundintheinteriorofthecellandwillbeexcludedfromtheaqueousenvironmentandwillinsteadbefoundinhydrophobiclocationssuchastheinteriorofamembrane.

Theremaining11aminoacidsarehydrophilic,witheitherpolarorchangedRgroups.Hydrophilicproteinstendtooccuronthesurfaceofproteins,therebymaximizingtheirinteractionswithwaterandotherchargedsubstances.

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Polyped7deForma7onPolypeptidesareformedbycovalentbondingbetweenaminoacids.Theprocessinvolvestheadditionofanewaminoacidtothechainbythedehydration/condensationreactions.ThecovalentC-Nbondlinkningthe2aminoacidsisknownasaPeptide

bond.

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Polypep7deForma7onTheformationofthepolypeptidehasdirectionality.It

alwayshasanaminogroupatoneendcalledtheNterminusandtheotherendhasacarboxylgroupcalledtheCterminus.

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LevelsofOrganiza7on

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PrimaryStructureTheprimarystructureofaproteinisasequenceof

aminoacidslinkedtogetherbypeptidebonds,formingapolypeptide.

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SecondaryStructureTheSecondarystructureinvolvesregionsofthe

polypeptidebeingassociatedtogetherbyH-bonds.Thecancoilintoahelixorformpleatedsheets.

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Ter7aryStructuresTheTertiarystructureisformedwhenregionsthesecondarystructureassociateduetodisulphide,ionic

andH-bondsorvanderwaalsandhydrophobicinteractions.Theseassociatesresultintheformation

ofa3Dstructure.

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QuaternaryStructuresTheQuaternaryStructureistheassociationof

multiplepolypeptidestoformafinalfunctionalprotein.

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Denatura7onofProteins Iftheproteinisexposedtodenaturingconditionse.g.

increaseintemp.orpH,thisdisruptsnoncovalentinteractionsbetweenaminoacidRgroupsandmakestheproteininactive.

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Renatura7on

Oncetheproteinisremovedfromtheextremeconditions,ThisallowsforrenewedinteractionsbetweentheRgroups.Thepolypeptidespontaneouslyreturnstoitsnativeconformationandregainsitsactivity.

Thesuggestthattheaminoacidsequencehasalltheinformationneededforthefoldingofthepolypeptide

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ProteinSynthesis

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GenesCodeforAminoAcidsThenucleotidesequenceofDNAwilldictatetheaminoacidsequenceofaprotein

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SickleCell

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SickleCellThisdiseaseoccurswhenGlutamate(Glu)ofthe

normalhemoglobinisreplacedbyValine(Val).Thiscausesthecelltobecomesickleandmorerigid.

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SickleCell

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OtherImportantProteinsHemoglobin

Hemoglobinistheiron-containingoxygen-transport

metalloproteinintheredbloodcells.Hemoglobininthebloodcarriesoxygenfromtherespiratoryorganstotherestofthebody(i.e.thetissues)whereitreleasestheoxygentoburnnutrientstoprovideenergytopowerthefunctionsoftheorganism,andcollectstheresultantcarbondioxidetobringitbacktotherespiratoryorganstobedispensedfromtheorganism.

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ImportantProteinsHemoglobin

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OxygenBindingCurveFetalHbhasahigheraffinitythanmaternalHb