1. Trang chủ
  2. » Luận Văn - Báo Cáo

Lecture biology (6e) chapter 5 campbell, reece

86 4 0

Đang tải... (xem toàn văn)

Tài liệu hạn chế xem trước, để xem đầy đủ mời bạn chọn Tải xuống

THÔNG TIN TÀI LIỆU

Thông tin cơ bản

Định dạng
Số trang 86
Dung lượng 1,58 MB

Nội dung

CHAPTER5THESTRUCTUREAND FUNCTIONOFMACROMOLECULES SectionA:Polymerprinciples Mostmacromoleculesarepolymers Animmensevarietyofpolymerscanbebuiltfromasmallsetofmonomers Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings Introduction ã Cellsjoinsmallerorganicmoleculestogetherto formlargermolecules ã Theselargermolecules,macromolecules,maybe composedofthousandsofatomsandweighover 100,000daltons ã Thefourmajorclassesofmacromoleculesare: carbohydrates,lipids,proteins,andnucleicacids Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings 1. Most macromolecules are polymers • Three of the four classes of macromolecules form  chainlike molecules called polymers • Polymers consist of many similar or identical building  blocks linked by covalent bonds • The repeated units are small molecules called  monomers • Some monomers have other functions of their own Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • The chemical mechanisms that cells use to make and  break polymers are similar for all classes of  macromolecules • Monomers are connected by covalent bonds via a  condensation reaction or dehydration reaction • One monomer provides  a hydroxyl group and  the other provides a  hydrogen and together  these form water • This process requires  energy and is aided  by enzymes.  Fig.5.2a Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Thecovalentbondsconnectingmonomersina polymeraredisassembledbyhydrolysis ã Inhydrolysisasthecovalentbondisbrokenahydrogen atomandhydroxylgroupfromasplitwatermolecule attacheswherethecovalentbondusedtobe ã Hydrolysisreactions dominatethe digestiveprocess, guidedbyspecific enzymes. Fig.5.2b Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings 2.Animmensevarietyofpolymerscanbe builtfromasmallsetofmonomers ã Each cell has thousands of different macromolecules • These molecules vary among cells of the same individual;  they vary more among unrelated individuals of a species,  and even more between species • This diversity comes from various combinations of  the 40­50 common monomers and other rarer ones • These monomers can be connected in various  combinationslikethe26lettersinthealphabetcanbe usedtocreateagreatdiversityofwords ã Biologicalmoleculesareevenmorediverse Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings CHAPTER5THESTRUCTUREAND FUNCTIONOFMACROMOLECULES SectionB:Carbohydratesư FuelandBuildingMaterial Sugars,thesmallestcarbohydrates,serveasfuelandcarbonsources Polysaccharides,thepolymersofsugars,havestorageandstructuralroles Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings Introduction ã Carbohydratesincludebothsugarsandpolymers ã Thesimplestcarbohydratesaremonosaccharidesor simplesugars • Disaccharides, double sugars, consist of two  monosaccharides joined by a condensation reaction • Polysaccharides are polymers of monosaccharides Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 1. Sugars, the smallest carbohydrates serve  as a source of fuel and carbon sources • Monosaccharides generally have molecular formulas  that are some multiple of CH2O • For example, glucose has the formula C6H12O6 • Most names for sugars end in ­ose • Monosaccharides have a carbonyl group and  multiple hydroxyl groups • If the carbonly group is at the end, the sugar is an aldose,  ifnot,thesugarsisaketose ã Glucose,analdose,andfructose,aketose,arestructural isomers Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Monosaccharidesarealsoclassifiedbythenumberofcarbonsin thebackbone ã Glucoseandothersixcarbonsugarsarehexoses • Five carbon backbones are pentoses and three carbon sugars are trioses • Monosaccharides may also exist as enantiomers.  • For example, glucose and galactose, both six­carbon aldoses,  differ in the spatial arrangement around asymmetrical carbons Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • While DNA has the information for all the cell’s  activities, it is not directly involved in the day to day  operations of the cell • Proteins are responsible for implementing the instructions  contained in DNA • Each gene along a DNA molecule directs the  synthesis of a specific type of messenger RNA  molecule (mRNA) • ThemRNAinteractswiththeproteinưsynthesizing machinerytodirecttheorderingofaminoacidsina polypeptide Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã TheflowofgeneticinformationisfromDNAư> RNAư>protein ã Proteinsynthesisoccurs incellularstructures calledribosomes ã Ineukaryotes,DNAis locatedinthenucleus, butmostribosomesare inthecytoplasmwith mRNAasan intermediary Fig.5.28 Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings 2.Anucleicacidstrandisapolymerof nucleotides ã Nucleicacidsarepolymersofmonomerscalled nucleotides ã Eachnucleotideconsistsofthreeparts:anitrogen base,apentosesugar,andaphosphategroup Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings Fig.5.29 Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Thenitrogenbases,ringsofcarbonandnitrogen, comeintwotypes:purinesandpyrimidines ã Pyrimidineshaveasinglesixưmemberedring ã Thethreedifferentpyrimidines,cytosine(C),thymine (T),anduracil(U)differinatomsattachedtothering ã Purinehaveasixưmemberedringjoinedtoafiveư memberedring ã Thetwopurinesareadenine(A)andguanine(G) Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Thepentosejoinedtothenitrogenbaseisribosein nucleotidesofRNAanddeoxyriboseinDNA ã Theonlydifferencebetweenthesugarsisthelackofan oxygenatomoncarbontwoindeoxyribose ã Thecombinationofapentoseandnucleicacidisa nucleoside ã Theadditionofaphosphategroupcreatesa nucleosidemonophosphateornucleotide Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Polynucleotidesaresynthesizedbyconnectingthe sugarsofonenucleotidetothephosphateofthe nextwithaphosphodiesterlink ã Thiscreatesarepeatingbackboneofsugarư phosphateunitswiththenitrogenbasesas appendages Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã ThesequenceofnitrogenbasesalongaDNAor mRNApolymerisuniqueforeachgene • Genes are normally hundreds to thousands of  nucleotides long • The number of possible combinations of the four  DNA bases is limitless • The linear order of bases in a gene specifies the  order of amino acids ­ the primary structure of a  protein • The primary structure in turn determines three­ dimensional conformation and function Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 3. Inheritance is based on replication of the  DNA double helix • An RNA molecule is a single polynucleotide chain • DNA molecules have two polynucleotide strands  thatspiralaroundanimaginaryaxistoforma doublehelix ã Thedoublehelixwasfirstproposedasthestructureof DNAin1953byJamesWatsonandFrancisCrick Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Thesugarưphosphatebackbonesofthetwo polynucleotidesareontheoutsideofthehelix ã Pairs of nitrogenous  bases, one from each  strand, connect the  polynucleotide chains  with hydrogen bonds • Most DNA molecules  have thousands to  millions of base pairs.  Fig. 5.30 Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Becauseoftheirshapes,onlysomebasesare compatiblewitheachother ã Adenine(A)alwayspairswiththymine(T)andguanine (G)withcytosine(C) ã Withthesebaseưpairingrules,ifweknowthe sequenceofbasesononestrand,weknowthe sequenceontheoppositestrand ã Thetwostrandsarecomplementary. Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Duringpreparationsforcelldivisioneachofthe strandsservesasatemplatetoordernucleotides intoanewcomplementarystrand ã Thisresultsintwoidenticalcopiesoftheoriginal doubleưstrandedDNAmolecule ã Thecopiesarethendistributedtothedaughtercells ã Thismechanismensuresthatthegenetic informationistransmittedwheneveracell reproduces. Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings 4.WecanuseDNAandproteinsastape measuresofevolution • Genes (DNA) and their products (proteins)  document the hereditary background of an  organism • Because DNA molecules are passed from parents to  offspring, siblings have greater similarity than do  unrelated individuals of the same species • This argument can be extended to develop a  moleculargenealogybetweenspecies Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Twospeciesthatappeartobecloselyưrelatedbased onfossilandmolecularevidenceshouldalsobe moresimilarinDNAandproteinsequencesthanare moredistantlyrelatedspecies ã Infact,thesequenceofaminoacidsinhemoglobin moleculesdifferbyonlyoneaminoacidbetweenhumans andgorilla ã Moredistantlyrelatedspecieshavemoredifferences. Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ... fructoseandisthemajortransportformofsugarsinplants. Fig .5. 5a Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã Whileoftendrawnasalinearskeleton,inaqueous solutionsmonosaccharidesformrings. Fig .5. 5 Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings... OnegroupofaminoacidshashydrophobicR groups. Fig .5. 15a Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings ã AnothergroupofaminoacidshaspolarRgroups, makingthemhydrophilic. Fig .5. 15b Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings... Chitinalsoforms thestructural supportforthe cellwallsof manyfungi Fig .5. 9 Copyrightâ2002PearsonEducation,Inc.,publishingasBenjaminCummings CHAPTER? ?5? ?THE STRUCTURE AND  FUNCTION OF MACROMOLECULES Section C: Lipids ­ Diverse Hydrophobic Molecules

Ngày đăng: 28/06/2021, 15:57