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macromolecules

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  • Macromolecules THEME 1

    WORKSHEETS

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    THREADS

    Organisation Selectivity Energy Flow Perpetuation Evolution Human Awareness

    The structure of DNA

    Chromosomes are made up of genes

    DNA and protein synthesis

    Structure and function of protein molecules in cells

    The importance of polysaccharides and lipids

    DNA replication

    Enzymes

    DNA and protein evidence for evolution

    Mutations

    Genetic manipulation

    Some social consequences of genetic

    manipulation

    Multiplying and sequencing DNA

  • KEY IDEAS

    Students should know and understand the following:

    M1. The chemical unit of genetic information in most organisms is DNA

    M2. The structural unit of information in the cell is the chromosome

    M3. The functional unit of information on the chromosome is the gene

    M4. The flow of information from DNA to protein is unidirectional in most organisms

    DNA RNA protein

    M5. The three-dimensional structure of a protein is critical to its function

    M6. Polysaccharides and lipids are important macromolecules in cells and organisms

    M7. Specific base-pairing is the mechanism of DNA replication

    M8. Enzymes are specific for their substrate

    M9. Molecular recognition is an important property for life processes

    M10. Enzymes increase reaction rates by lowering activation energy

    M11. Macromolecules are used as energy reserves

    M12. DNA carries genetic information from one generation to the next

    M13. The universal presence of DNA is strong evidence for the common ancestry of all living things

    M14. DNA and protein sequences usually show greater similarity between closely related groups of organisms than between distantly related groups

    M15. Change in the base sequence of DNA can lead to the alteration or absence of proteins, and to the appearance of new characteristics in the descendants

    M16. Human beings can manipulate DNA

    M17. Human beings can sequence even small amounts of DNA

    ( SSABSA Stage 2 Biology Curriculum Statement 2006, p22-24 and used with permission. Teachers and students are advised to check the website www.ssabsa.sa.edu.sa for any changes.)

  • SACE 2 BIOLOGY Essentials WORKBOOK

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    6

    T

    G

    A

    G

    A T

    G

    G

    G

    A

    C

    C

    T

    C

    C

    T

    T

    TA

    A

    A

    C

    T

    C

    G

    A

    Worksheet 1 The structure of DNA DNAstandsfordeoxyribonucleicacid.Thismoleculeisfoundprimarilyinthenucleusofcells.Itisadoublestrandedmoleculewiththestrandswoundaroundeachothertoformadoublehelix.Themoleculeismadeupofrepeatingunitscallednucleotides.Asinglenucleotideismadeupofthreecomponents:adeoxyribosesugar,aphosphateandanorganicbase.Thediagrambelowisarepresentationof2nucleotidesbondedtogether.

    A T

    Phosphate

    Deoxyribose sugar

    Weak hydrogen bonds between bases

    Bases

    TherearefourorganicbasesfoundinDNA:Adenine,Thymine,GuanineandCytosine.ThelettersA,T,GandCrepresentthesebases.AsinglestrandofDNAisasequenceofnucleotidesjoinedtogetherwithalternatingphosphateandsugarcomponents.Thedoublehelixmoleculeconsistsoftwocomplementarystrandsthatarejoinedbyhydrogenbondsbetweenthebases.Thebasesalwayspairinspecificways:AdeninealwaysbondswithThymineGuaninealwaysbondswithCytosineThyminealwaysbondswithAdenineCytosinealwaysbondswithGuanineTheadjacentdiagramshowsthedoublehelicalmodelforDNAfirstproposedbytwoscientistsWatsonandCrickin1953.

    1. Writeaconcisestatementtoexplaineachofthefollowingterms: complementary ...

    DNA ...

    macromolecule ...

    monomer ...

    nucleicacid ...

    nucleotide ...

    organic ...

    polymer ...

    base ...

    deoxyribosesugar ...

    phosphate ...

  • Worksheet 1 THE STRUCTURE OF DNA

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    7

    Sugar Phosphate Sugar Phosphate Sugar Phosphate Sugar Phosphate

    Base Base Base Base

    A T

    C

    B

    A

    D

    2. ThefollowingsequenceofbaseswasfoundinasegmentofDNA

    A A G G C T T G C Writethesequenceofbasesthatwouldbefoundinthecomplementarystrand. .

    3. NamethefourmajororganicbasesfoundinDNA.

    .....4. WritedownthefourpossiblebasepairingsinDNA.

    ....5. IfasequenceofDNAhas30%guaninebasesinitwhatpercentageofthyminewouldtherebe?

    ....6. Refertothediagrambelow.

    (a)CircleanucleotideintherepresentationofastrandofDNAshownabove.

    (b)Howmanynucleotidesareshowninthediagram?.7. UsethefiguretolabelABCandDinthediagrambelow.

    A

    B ....

    C ....

    D ....

  • SACE 2 BIOLOGY Essentials WORKBOOK

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    8

    2 3 7 9 11 12 14 17Familial

    Colon CancerRetinitis

    PigmentosaCystic Fibrosis

    MalignantMelanoma

    Sickle CellAnemia

    PKU Alzheimer'sDisease

    BreastCancer

    Worksheet 2 Chromosomes are made up of genes ChromosomesarethreadlikestructuresmadeupofDNAandproteinscallhistones.Thesestructuresarefoundinthenucleusofeukaryoticcellsandarevisibleasthecellsstarttodivide.Thechromosomenumberisconstantforeachspecies,e.g.46inhumans,48inachimpanzee,40inamouseand38incabbage.ChromosomesinnondividingcellsaresinglestrandedandtheDNAisnotcondensed,thatis,theDNAisspreadouttomakeiteasiertoaccessgenesintranscription,animportantprocessinproteinsynthesisandreplication,whereanothercopyoftheDNAismade.WhenthechromosomesarevisibleduringtheProphasestageofmitosisand/ormeiosistheyappeardoublestranded.ThisdoublinghasoccurredastheDNAhasreplicatedinorderthatnewcellscanreceivetheircomplementofDNA.Ageneistheunitofheredity.GenesrepresentsequencesofthebasesATGandConchromosomesandcodeforproteinmoleculesorpartsofproteinmolecules.Eachgeneisfoundonaparticularchromosome.Genesprescribethefeaturesofanorganism:greeneyes,skincolourortheshapeofanose.Inahumanwith46chromosomesitisthoughtthattherearearound40,000genes,eachchromosomecontaininghundredsorthousandsofgenes.Asinglegeneusuallycontainsbetween300toseveralthousandbases.Eachgenehasastartandafinishtosignalwheretranscriptionbeginsandends.Thediagrambelowshowsschematicrepresentationsofsomehumanchromosomesandsomeofthegenelocationsthathavebeenidentified.

    The human genome project. Thisisaprojectthatwasfirstproposedaround1987.Itsaimwastomaptheentiresequenceofgenestochromosomesandsequencethehumangenome.Thefigureaboveillustratessomeoftheknowngenelocations(loci).InAdelaideagroupofscientistsattheWomenandChildrensHospitalisinvolvedinstudyingchromosome16.Thisoverallmappingisamajorundertakingasthereareapproximately3billionbuildingblocksornucleotidesinthetotalgenome.ThefirststagewascompletedinaboutJune2000.Thisphotographshowsatypicalsetofhumanchromosomes,whichwastakenfromapreparedslideusingalightmicroscope.Theimageshavebeencutoutandpastedtogethertoshowthehomologouspairs.Untilrecentlythiswasdonewithscissors,itisnowdonewithcomputersoftwareTheyaregenerallynumberedandarrangedfromlongesttoshortest.Thesexchromosomesarebottomrightofthisphoto.Thisisthemalesetofchromosomesorkaryotype.Afemalehastwocopiesofthelonger(X)sexchromosomeinsteadofonelong(X)andoneshort(Y).

  • Worksheet 2 CHROMOSOMES ARE MADE UP OF GENES

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    9

    1. Writeaconcisestatementtoexplaineachofthefollowingterms:. chromatid ...

    chromosome ...

    gene ...

    genome ...

    2. Inwhatorganellearethechromosomesfoundineukaryoticcells?3. Whyarethechromosomesnotusuallyvisibleinnondividingcells?

    ...

    ...

    4. ExplainthedifferencesbetweenDNA,genes,chromosomes.

    ...

    ...

    5. Whatdoesitmeantosaythatageneislinkedtoachromosome?

    ...

    ...

    6. Explainthesignificanceofdifferentspecieshavingdifferentnumbersandtypesofchromosomes?

    ...

    .....

    7. Approximatelyhowmanygenesarethere; (a)ononehumanchromosome? ....

    (b)inthehumangenome? ....

    8. ScientistshaveknownforaconsiderableperiodoftimethatthegeneforcolourblindnessisontheXchromosome.

    (a)SuggesthowitwasdiscoveredthatthiswaslinkedtotheXchromosome.

    ...

    ...

    (b)GeneslikethisaresaidtobeXlinkedandthecharacteristicsaresaidtobesexlinked.Explainwhythisisso....

    ...

    9. Explainwhatitmeanstosaythatthestructuralunitofinformationinanorganismisthechromosome.

    ...

    ...

    ...

    ...

  • SACE 2 BIOLOGY Essentials WORKBOOK

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    10

    Worksheet 3 DNA and protein synthesis GenesontheDNAcodeforaspecificsequenceofaminoacids(aa)thatcompriseapolypeptide.Severalpoypeptidesusuallymakeupaprotein.TheycanalsocodefortheproductionofanRNAmolecule.Proteinsynthesisrequirestwosteps:transcriptionandtranslation.Threemainnucleicacidsareinvolved.DNA: providesthetemplatefortheproductionofthemRNA.mRNA: transcribedfromtheDNAandprovidesasequenceofcodonsthatareabletobe

    translatedintoasequenceofaminoacidsontheribosomes.tRNA: therearemorethan20differenttypesofthese,eachonecapableofcarryingonlyone

    typeofaminoacid.

    Transcription ThisprocessoccursinthenucleusofacellandiswheretheDNAtemplateactsasacodetotranscribeagenesegmentofDNAbasesintoaworkingcopyofmRNA.TheenzymeinvolvediscalledRNAPolymerase.Thediagrambelowshowstheprocessoftranscription.

    T A

    GC

    AT

    C C

    T A

    T A

    C G

    T

    C G

    T A

    T A

    C G

    T A

    A

    G

    G

    A

    A

    C

    C

    T

    T

    G

    U

    U

    C

    C

    C

    U

    U

    CC

    CU

    UC

    AC

    G

    U

    GA

    CU

    RNA polymerase

    DNA Template

    Growing mRNA strand

    Nucleotides used to assemble the mRNA

    mRNAnucleotidesinthenucleusarebindingtotheexposedDNAbasestoformaworkingcopyofthegenethatwillbeabletobetranslatedontheribosomestoformprotein.

    Translation IsaprocesswherethecodonsequenceonthemRNAistranslatedintoanaminoacidlanguage.tRNAmoleculescarryspecificaminoacidsintopositionastheanticodonofthetRNAlinkswiththecodononthemRNA.Thenextdiagramshowstheprocessoftranslation.

  • Worksheet 3 DNA AND PROTEIN SYNTHESIS

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    11

    Inthediagramabove,leucineandserinearethefirsttwoaminoacidsthatarejoinedtogetherbypeptidebondstostartthepolypeptideorprotein.

    The steps involved in protein synthesis can be set out as follows. 1. ThedoublehelixoftheDNAunwindsandunzipsattherequiredgenesiteexposingthenitrogenous

    basesonthetemplate.

    2. mRNAnucleotidebases(AUGC)attachtotheexposedDNAbaseswiththeassistanceoftheenzymeRNApolymerase.

    3. OncethesequenceforthemRNAhasbeencompleted,themRNAisreleasedandmovesoutofthenucleusintothecytoplasm.

    4. TheDNAstrandswillrejoinandrecoilthemselvestoformthedoublehelix.

    5. ThemRNAmoleculeattachestotheribosomesinthecytoplasm.

    6. SpecificaminoacidscombinewiththeirappropriatetRNAmolecules.

    7. TheribosomemovesalongthemRNAmoleculeattachingtheappropriatetRNAanticodontothecodononthemRNA.

    8. Theaminoacidsjointogethertoformapolypeptidesequence.

    9. Whenastopcodonisreachedthetranslationiscomplete.

    10. Theproteinbreaksawayandisreadyforusewithinthecell,ortobepackagedandsecretedfromthecell.

    1 Writeaconcisestatementtoexplaineachofthefollowingterms: aminoacid

    anticodon

    codon

    RNApolymerase

    mRNA

    ribosome

  • SACE 2 BIOLOGY Essentials WORKBOOK

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    12

    transcription

    translation

    tRNA

    2. TohelpyouidentifydifferencesbetweenDNA,mRNA,andtRNA,completethefollowingstatementsbywritingtheappropriatenucleicacid(s)aftereachone.

    a. issinglestranded ..

    b. hasadoublehelicalstructure ..

    c. isonlyfoundinthecytoplasm ..

    d. isfoundprimarilyinthenucleusofacell ..

    e. containsthebasethymine ..

    f. containsthebaseuracil ..

    g. isinvolvedintheprocessofreplication ..

    h. carriesaminoacidstotheribosomes ..

    i hastripletsofbasescalledcodons ..

    j isfoundinboththenucleusandcytoplasm ..

    k hasthreebaseswhichcomprisetheanticodon ..3. Explaintheroleofthefollowingintheprocessofproteinsynthesis: DNA ..

    ...

    mRNA ..

    ...

    tRNA ..

    ...

    aminoacids..

    ...

    ribosomes ..

    ...

    mitochondria.

    ..

    4. Explainthedifferencebetween: a)transcriptionandtranslation

    b)acodonandananticodon

  • Worksheet 3 DNA AND PROTEIN SYNTHESIS

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    13

    5. Usethediagrambelow,whichshowsasummaryoftheprocessofproteinsynthesis,towritethenamesandrolesofthestructureslabelled:

    J

    CYTOPLASM

    LA UAU AU

    C AUG UA K

    Leucine Serine M

    NUCLEUS

    AC

    G

    U

    GA

    CU

    A

    B

    C

    D

    E

    F

    GH

    I

    T A

    GC

    AT

    C C

    T A

    T A

    C G

    T

    C G

    T A

    T A

    C G

    T A

    A

    G

    G

    A

    A

    C

    C

    T

    T

    G

    U

    U

    C

    C

    C

    U

    U

    CC

    CU

    UC

    A

    B

    C

    D

    E

    F

    G

    H

    I

    J

    K

    L

    M

  • SACE 2 BIOLOGY Essentials WORKBOOK

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    14

    6. Thetablebelowshowswhichcodonscarrytheinformationforeachaminoacid.

    Thetablebelowshowsthenamesoftheaminoacidstogetherwiththeabbreviationsusedinthetableabove.ala= alanine gly= glycine pro= proline arg= arginine his= histidine ser= serine asn= asparagine ile= isoleucine thr= threonine asp= asparticacid leu= leucine trp= tryptophan cys= cysteine lys= lysine tyr= tyrosinegln= glutamine met= methionine val= valineglu= glutamicacid phe= phenylalanine

    Now,usethetableofthegeneticcodeandnamesoftheaminoacidsgiventohelpyoucompletethefollowingtable.

    DNAbasetriplets AGA ________ ________ ________

    mRNAcodons ________ CGG ________ ________

    tRNAanticodons ________ ________ CUG ________

    aminoacidcodedfor ________ ________ ________ methionine

  • Worksheet 4 STRUCTURE AND FUNCTION OF PROTEINS

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    15

    Polypeptidechain

    Polypeptidechain

    Heme

    ala

    gly

    leu

    val

    lys

    PRIMARY STRUCTURE

    SECONDARYSTRUCTURE

    TERTIARY STRUCTURE

    QUATERNARYSTRUCTURE

    Worksheet 4 Structure and function of protein molecules Proteinmoleculesarelargepolymersmadeupofabout20commonbuildingblockscalledaminoacidslinkedtogether.Organismstypically,havethousandsofthesemolecules.Humansarethoughttohavebetween50,000100,000differentproteins,eachonewithauniquethreedimensionalstructurethatiscriticalforitsparticularfunction.Proteinscanbeplacedinto2maingroups,fibrousorstructuralproteins,andglobularproteins.

    Protein structure can be studied at four levels Primarystructurethesequenceofaminoacidslinkedbypeptidebonds.Eachproteinischaracterised

    byitsownuniquenumber,typeandsequenceofaminoacids.Typicallyproteinsaremadeupofhundredstothousandsofaminoacids,haemoglobin,atransportprotein,issome400timesbiggerinsizethanaglucosemolecule.

    Secondarystructurethecoilingorfoldingofthepolypeptidechain. Tertiarystructurethethreedimensionalstructure,whichisimportantforbinding. Quaternarystructureappliestothoseproteinswithmorethanonepolypeptidestrand.Itisthetertiarystructureofeachspecificproteinthatdeterminesitsspecificfunction.Ifthedelicatethreedimensionalshapeofaproteinisaltered,itusuallyfollowsthatthefunctionofthatproteinisalsoinhibited,thisiscalleddenaturation.Thediagrambelowgivesadiagrammaticrepresentationofthedifferentlevelsofstructureinamoleculeofhaemoglobinwhichisaproteinfoundinblood.

    Thestructuralproteinsaremorefibrousinnatureandtendtohaverepeatingunitsofaminoacidsequences,whereastheglobularproteinseachhavetheirownuniquesequencesgivingthemtheirparticularshapethatissovitalfortheirfunction.

    Types of proteins. Proteinscanbeplacedintogroupsdependingontheirparticularrolesintheorganism.

    Structural Examplesincludethosethatmakeupligamentsandtendons,whileothersassistinmovement,forexamplemuscleproteins.Keratinisanimportantstructuralproteinfoundinorganisms,itmakesuptheouterlayerofskin,andisthemaincomponentofhair,nails,wool,beaksandfeathers.Proteinsembeddedinthecellmembranearevitalfortheefficientfunctioningofcells.Somehaverolesinactingaschannelproteinsallowingcertainmoleculestoenterorleavecells,butnotothers.Otherproteinsactasreceptorproteinsthatcanbindtochemicalslikehormones,andthusbringaboutaparticularresponse.

    Defence Specificproteinmolecules,calledantibodies,arereleasedfromwhitebloodcellsandhavearoleintheinactivationanddestructionofforeignantigenmoleculesthatmayinvadeourtissues.Theuniqueshapeoftheproteinantibodymeansthattheactionofeachantibodyisspecificforaparticularantigen;oneparticularantibodycanonlybindwithandinactivateoneparticularantigen.

  • SACE 2 BIOLOGY Essentials WORKBOOK

    CrierieA.andGreigD.2008Allrightsarereserved,copyingisprohibitedbylaw.

    16

    Hormone messenger molecule

    Lipid bi-layer

    Receptor molecule embedded into the bi-lipid layer of cell membrane

    Binding leads to activation

    Communication Certainmolecules,includingsomehormones,bringabouttheirspecificactionbybindingtoothermolecules.Whenthehormoneinsulinbindstoreceptorproteinsinthecellmembrane,thecellmembraneincreaseitspermeabilitytoglucoseandthecelltakesupmoreglucosetostoreasglycogen.Thediagrambelowrepresentsthebindingofahormonetoasurfacereceptor.

    Transport Haemoglobinisaproteinmoleculefoundinsidehumanredbloodcells.Ithasaspecificroleinthetransportofoxygenmoleculestothetissuesofthebody.Theparticularshapeofthemoleculemakesitidealforthereversiblebindingthatoccurswithoxygen.

    The control of metabolic reactions. Allreactionsinsidecellsneedspecificenzymemoleculestoensurethattheyproceed.Enzymesareproteinmoleculeswithaspecificshapethatiscriticalforthebindingofthereactantorsubstratemolecules.Thethreedimensionalshapeoftheproteingivesrisetoanactivesiteontheenzymewhereaninducedfitbindingoccurs.

    1. Writeaconcisestatementtoexplaineachofthefollowingterms: antibody

    antigen

    complementarystrand..

    denature

    enzyme

    haemoglobin

    hormone

    insulin

    polypeptide

    protein

    surfacereceptor