生物化学作业.docx

生物化学作业.docx

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生物化学作业

SectionA　andB

1.Thetypicalstructureofaprokaryoticcellandaeukaryotecell?

1.Typicalstuructures：

（drawapicturetodescribetypicalsturcuturesofbothcellsisalsosuggested）

Prokaryotecell:

Mesosome,Nucleoid

Eukaryoticcell：

Nucleus，Plasmamembrane，Endoplasmicreticulum，Golgiapparatus，Mitochondria，Chloroplasts，Lysosomes，Peroxisomes，Cytosol

2.Themainfunctionofaprotein

Catalysis:

--LDH（lactatedehydrogenase,intheglycolyticpathway）

--DNApolymerase（inDNAreplication）

Transport:

--hemoglobin（transportsO2intheblood）

--lactosepermease（transportslactoseacrossthecellmembrane）

Structure:

--collagen（connectivetissue）

--keratin（hair,nails,feathers,horns）

Motion:

--myosin（muscletissue）

--actin（muscletissue,cellmotility）

3.Rightdownthe20standardaminoacids,andsummarizethemainpropertiesofmostα-aminoacids.

Drawthestructuresof20standardaminoacids,Theα-carbonhasalwaysfoursubstituentsandistetrahedral.All（exceptproline）haveanacidiccarboxylgroup,abasicaminogroup,andanhydrogenconnectedtothecarbon,eachaminoacidhasanuniquefourthsubstituentRwiththeexceptionofglycine（thefourthsubstituentisalsohydrogen）

4.AccordingtothestructureofRresidue,howtoclassifyacidandbasicAAS?

Aminoacidsaredipolarionsinaqueoussolutionandareamphoteric,thepropertyofAASisvariedinthebufferbasedonthetitrationexperiment.

AccordingtothedifferentstructureofRresidueinAAS,theyareclassifiedinto:

“Acidic”aminoacids:

containingadditionalcarboxylgroupswhichareusuallyionized.Thoseaminoacidswithanionizableside-chain（Asp,Glu,Arg,Lys,His,Cys,Tyr）haveanadditionalacid–basegroup.

“Basic”aminoacids:

containingpositivelychargedgroupssuchasArgandLys.

5.Whatisthetypicalstructureinthesecondarystructureofaprotein?

Secondarysturctureinaproteinreferstotheregularfoldingofregionsofthepolypeptidechain.Thetwomostcommontypesarethea-helix,𝛽-sheet.

6.Whatisthenoncovalentinteractionbetweensidechainsthatholdthetertiarystructuretogether?

Noncovalentinteractionbetweensidechainsthatholdthetertiarystructuretogether:

vanderWaalsforces,hydrogenbonds,electrostaticsaltbridges,hydrophobicinteractions.

7.Definitions:

1.Flowcytometry:

Individualcellscanbeidentifiedusingaflowcytometer.Antibodies,coupledtofluorescentcompounds,thatbindtomoleculesonthesurfaceofparticulartypesofcellscanbeusedtoseparatecellsfromeachotherinafluorescence-activatedcellsorter（FACS）.

2.Enantiomers:

FourdifferentgroupsarrangedtetrahedrallyaroundtheCatomandthuscanexistineithertheDorLconfiguration.Thesetwoenantiomersarenonsuperimposablemirrorimagesthatcanbedistinguishedonthebasisoftheirdifferentrotationofplane-polarizedlight.

3.Peptidebond:

Thepeptidebondisacovalentbondbetweentheα-aminogroupofoneaminoacidandtheα-carboxylgroupofanother.

4.Primarystructure:

Thelinearsequenceofaminoacidsjoinedtogetherbypeptidebondsistermedtheprimarystructureoftheprotein.Thepositionofcovalentdisulfidebondsbetweencysteineresiduesisalsoincludedintheprimarystructure.

5.Secondarystructure:

Secondarystructureinaproteinreferstotheregularfoldingofregionsofthepolypeptidechain.

6.Tertiarystructure:

Tertiarystructureinaproteinreferstothethree-dimensionalarrangementofalltheaminoacidsinthepolypeptidechain.Thisbiologicallyactive,nativeconformationismaintainedbymultiplenoncovalentbonds.

7.Quaternarystructure:

Ifaproteinismadeupofmorethanonepolypeptidechainitissaidtohavequaternarystructure.Thisreferstothespatialarrangementofthepolypeptidesubunitsandthenatureoftheinteractionsbetweenthem.

8.Protheticgroups:

Ametalorcoenzymethatiscovalentlyattachedtotheenzymeiscalledaprostheticgroup.

9.Motif:

aregroupingsofsecondarystructuralelementsthatfrequentlyoccuringlobularproteins.Theyoftenhavefunctionalsignificanceandcanrepresenttheessentialpartsofbindingorcatalyticsitesthathavebeenconservedduringtheevolutionof

proteinfamiliesfromacommonancestor.

10.Domain:

Structurallyindependentunits,orfamiliesthatareconnectedbysectionswithlimitedhigherorderstructurewithintheevolutionsamepolypeptide.

11.Ionexchangechromatography:

isachromatographyprocessthatseparatesionsandpolarmoleculesbasedontheiraffinitytotheionexchanger，proteinsareseparatedonthebasisoftheiroverall（net）charge.

12.Affinitychromatography:

Affinitychromatographyexploitsthespecific,highaffinity,noncovalentbindingofaproteintoanothermolecule,theligand.thistechniqueexploitsthespecific,oftenunique,bindingpropertiesoftheprotein,itisoftenpossibletoseparatetheproteinfromamixtureofhundredsofotherproteinsinasinglechromatographicstep.

HomeworkforsectionC,D

1.Writedownthefollowingdefinitions:

Activesite,prostheticgroups,isoenzyme,freeenergychange,monoclonalantibody.

Activesite:

Theregionoftheenzymethatbindsthesubstrate,totransformsitintoproduct.

Coenzymes:

Manyenzymesrequirethepresenceofsmall,nonproteinunitsorcofactorstocarryouttheirparticularreaction.Acomplexorganicmoleculecalledacoenzyme.

Prostheticgroups:

cofactorsmaybeinorganicionsorcomplexorganicmolecules,someofcofactorsthatcovalentlyattachedtotheemzymeiscalledprotheticgroups.

Isoenzyme:

isoenzymesaredifferentformsofanenzymewhichcatalyzethesamereaction,butwhichexhibitdifferentphysicalorkineticproperties.

Freeenergychange:

ThedifferenceinenergylevelbetweenthesubstratesandproductistermedthechangeinGibbsfreenergy（ΔG）.

Monoclonalantibody:

Antibodyproducedbyasinglecloneofcellsisamonoclonalantibody,whichareidenticalandbindtothesameantigenicsitewithidenticalbindingaffinities.

Complement:

Thecomplementsystemisapartoftheimmunesystemthatenhances（complements）theabilityofantibodiesandphagocyticcellstoclearmicrobesanddamagedcellsfromanorganism,promotesinflammation,andattacksthepathogen'splasmamembrane.（不需要完全记住，理解即可）

2.Listthesixmainclassesofenzymesclassifiedbythereactiontheycatalyze.

3.Whatisenzymevelocity?

Pleasesetthelimitationfactorsthatinfluencetheenzymevelocity.

Enzymevelocityreferstotherateofanenzyme-catalyzedreaction.Thelimitationfactorsincludessubstrateconcentration;enzymeconcentration;temperature;pH.

4.Whatisthefeedbackregulation?

Andpleasesetanexampleforfeedbackregulationinitsimplicationinmetabolicregulation.

Afeedbackregulationisusuallyfoundinmetabolicregulationwhenanenzymeearlyoninthepathwayisinhibitedbyanend-productofthemetabolicpathwayinwhichitisinvolved.

5.Whatisthebasicstructureofanallostericenzyme?

Allostericenzymes are enzymes thatchangetheir conformationalensemble uponbindingofan effector,whichresultsinanapparentchangeinbindingaffinityatadifferentligandbindingsite.（Inallostericenzmes,thebindingofasubstratemoleculetooneactivesiteaffectsthebindingofsubstratemoleculestootheractivesitesintheenzyme;thedifferentactivesitesaresaidtobehavecooperativelyinbindingandactingonsubstratemolecules.）

6.Whatisthemainfunctionofimmunesystem?

Theimmunesystemhastwomainfunctions;torecognizeinvadingpathogensandthentotriggerpathwaysthatwilldestroythem.

7.WhatisthebasicstructureandmainfunctionofIgG?

EachIgGantibodymoleculeconsistsoffourpolypeptidechains（twoidenticallightchainsandtwoidenticalheavychainsjoinedbydisulfidebonds）andhastwoantigen-bindingsites.Itprovidesthemajorityofantibody-basedimmunityagainstinvadingpathogensandactivatecomplementandtriggermacrophages,butistheonlyantibodythatcanpassthroughtheplacentaandsoprovideimmunologicalprotectionforthefetus.

8.Whatistheclonalselectiontheoryinhumoralimmunesystem?

Youcansimplydescribethisprocessbyapicture.

Alargenumberofantibody-producingcellsexistinananimalevenbeforeitencountersaforeignantigen,eachcellproducingonlyonespecificantibodyanddisplayingthisonitscellsurface.Anantigenbindstocellsthatdisplayantibodieswithappropriatebindingsitesandcausesproliferationofthosecellstoformclonesofcellssecretingthesameantibodyinhighconcentration.

9.Pleasesettwoexamplesformonoclonalantibodyimplicationinclinicaldiagnosisandtherapy.

Anyspecificexampleinmonoclonaltherapyordiagnosisyoucanfindinthefollowingfigure:

SectionE

1.Describethebasicstructureofcellmembrane?

Whatisthemaincomponentofmembranelipids?

Allmembranescontaintwobasiccomponents:

lipidsandproteins.Somemembranesalsocontaincarbohydrate.Thecompositionoflipid,proteinandcarbohydratevariesfromonemembranetoanother.Therearethreemajortypesoflipid:

theglycerophospholipidsthesphingolipidsandthesterols.

2.Whatisthetypicalstructurewithinanintergralprotein?

Mostintegralproteinshaveoneormoreregionsofthehydrophobicpolypeptidechainthattraversethelipidbilayer.Theseregionsconsistmainlyofaminoacidswithhydrophobicside-chainsthatfoldintoanα-helixandinteractnoncovalentlywiththesurroundinglipids.

3.Describetheprocessofglucosetransportintoerythrocytes（anexampleinpassivetransport）,andglucosetransportintointerstinalepithelialcells（anexampleinactivetransport）,andexplainthemaindifferencebetweenthem.

Homeworkforsectio