TheMoleculesofLifeTheelementsinvolvedinlifeprocessescan,anddo,formmillionsofdifferentcompounds.Thankfully,thesemillionsofcompoundsfallintofourmajorgroups:carbohydrates,proteins,lipids,andnucleicacids.Thoughallofthesegroupsareorganizedaroundcarbon,eachgrouphasitsownspecialstructureandfunction.分子的生活脂類，核酸.全部這些四周都是由碳的構造組成，每組hasits？擁有特別的構造和功能。CarbohydratesCarbohydratesarecompoundsthathavecarbon,hydrogen,andoxygenatomsinaratioofabout1:2:1.Ifyou’restuckonanSATIIBiologyquestionaboutwhetheracompoundisacarbohydrate,justcountuptheatomsandseeiftheyfitthis ratio.Carbohydrates are often sugars, which provide energy forcellularprocesses.Likeallofthebiologicallyimportantclassesofcompounds,carbohydratescanbemonomers,dimers,orpolymers.Thenamesofmostcarbohydratesendin“-ose”:glucose,fructose,sucrose,andmaltosearesomecommonexamples.碳水化合物1：2：1。假設在SAT2生物學考比。碳水化合物往往是供給能源給細胞的過程的糖類。像全部的生物重要化合物的種類如：碳水化合物，單體，二聚體，或者聚合體。大局部碳水化合物名字的后面有“-OSE”：葡萄糖，果糖，蔗糖，麥芽糖是一些常見的例子。MonosaccharidesCarbohydratemonomersareknownasmonosaccharides.Thisgroupincludesglucose,C6H12O6,whichisakeysubstanceinbiochemistry.Sugarsthatananimaleatsareconvertedintoglucose,whichisthenconvertedintoenergytofueltheanimal’sactivitiesbyrespiration(s eeCellProcesses).Glucosehasacousincalledfructosewiththesamechemicalformula.Butthesetwocompoundshavedifferentstructures:Glucose and fructose differ in one importantway: glucose has adouble-bondedoxygenonthetopcarbon,whilefructosehasitsdouble-bondedcarbononthesecondcarbon.Thisdifferenceismostapparentwhenthetwomonosaccharidesareintheirringforms.Glucosegenerallyformsahexagonalring(sixsided),whilefructoseformsapentagonalring(fivesided).Whereasfructoseisthesugarmostoftenfoundinfruits,glucoseismostoftenusedasthemajorsourceofenergyforcellularactivities.單糖碳水化合物單體被稱為單糖。單糖包括葡萄糖，酒精，這是生物化學中一個關鍵呼吸作用消耗的能量。葡萄糖與果糖具有一樣的化學分子〔C6H1206)但是這兩個化合物具有不同的構造(我沒記錯的話是一個有醛基，一個沒有〕〔6片面〕，而果糖形成了一個五角環〔5片面〕。在水果中的經常發下的糖是果糖，葡萄糖是作為主要的能源來源，為細胞活動供給能量。DisaccharidesDisaccharidesarecarbohydratedimers.Thesedimersareformedfromtwomonomers by dehydrationsynthesis. Any two monosaccharides can form adisaccharide.Forexample,maltoseisformedbythedehydrationsynthesisoftwoglucosemolecules.Sucrose,commontablesugar,comesfromthelinkageofonemoleculeofglucoseandoneoffructose.二糖來說，麥芽糖是由脫水合成二葡萄糖分子。蔗糖，淀粉，是由葡萄糖和果糖組成的。PolysaccharidesPolysaccharidescanconsistofasfewasthreeandasmanyasseveralthousandmonosaccharides.Dependingontheirstructureandthemonosaccharidestheycontain,polysaccharidescanfunctionasameansofstoringexcessenergyorprovidestructuralsupport.Whencellsingestmorecarbohydratesthantheyneedforfuel,theylinkthesugarstogethertoformpolysaccharides.Thestructureofthesepolysaccharidesisdifferentinplantsandanimals:inplants,polysaccharidestaketheformofstarch,whereasinanimals,theyarelinkedinastructurecalledglycogen.Polysaccharidescanalsohavestructuralrolesinplantsandanimals.Cellulose,whichformsthecellwallsofplantcells,isastructuralpolysaccharide.Inanimals,thepolysaccharidechitinformsthehardouterarmorofinsects,crabs,spiders,andotherarthropods.Manyfungialsousechitinasastructuralcarbohydrate.多糖以多糖可以儲存過剩的能源或供給構造性支持。構，植物和動物的多糖不一樣：在植物中，多糖存在形式是淀粉，而在動物，他們鏈接一起后存在形式是糖元。維素就是是一個構造性的多糖。在動物方面，多糖甲殼素形式鎧甲如昆蟲，螃蟹，蜘蛛，和其他節肢動物的殼。很多真菌也利用甲殼素作為一個構造性碳水化合物。ProteinsMorethanhalfoftheorganiccompoundsincellsareproteins,whichplayanimportantfunctioninalmosteverycellularprocess.Proteins,forexample,providestructuralsupporttothecellinthecytoskeletonandmakeupmanyofthehormonesthatsendmessagesaroundthebody.Enzymes,whichregulatechemicalreactionsinthecell,arealsoproteins.蛋白質的骨架和輸送激素到身體的各個部位。在細胞中酶調整化學反響，也是靠蛋白質〔由于酶就是一種蛋白質〕AminoAcidsProteinsaremadeupofmonomerscalledaminoacids.Thenamesofmany,butnotall,aminoacidsendin-ine:methionine,lysine,serine,etc.Eachaminoacidconsistsofacentralcarbonatomattachedtoasetofthreedesignatedgroups:anatomofhydrogen(–H),anaminogroup( –NH2),andacarboxylgroup( –COOH).Thefinalgroup,designated( –R)inthediagrambelow,variesbetweendifferentaminoacids.ItispossibletomakeaninfinitenumberofaminoacidsbyattachingdifferentcompoundstotheRpositionofthecentralcarbon.However,only20typesofRgroupsexistinnature,sothereareonly20naturallyoccurringaminoacids.氨基酸氨基酸是蛋白質的單體。他的名稱很多，都以INE結尾：蛋氨酸，賴氨酸，絲氨酸等，每個氨基酸組成的中心碳原子上都連有3個基團這是不會變的：1原子氫〔-H〕的，一氨基酸組〔-NH2〕，和一個羧基〔-COOH〕。最終一組，都是R基〔-R〕在如以下圖，R這也就是說可以有很多種的氨基酸，只要中心碳的支鏈上有不同的R基。但是，在性質上只有20R20種氨基酸。多肽這20個氨基酸的局部或全部制成全部的蛋白質的鏈-NH2與-OH之間稱作一個肽鍵2個集團組合到一起的過程就叫脫水縮合氨基酸為其主要構造，某一特定蛋白質有特定的氨基酸序列，這是眾所周知。每一個蛋白質在三維立體空間中經過一系列的過程如卷等這些都是都預定好的的2級〔初步繞組和卷取〕和三級構造〔整體折疊〕。在苛刻的條件，如高溫或極端的pH性”。PolypeptidesAllproteinsaremadeofchainsofsomeorallofthese20aminoacids.Thebondformedbetweentwoaminoacidsbydehydrationsynthesisisknownasapeptidebond.Aparticularproteinhasaspecificsequenceofaminoacids,whichisknownasitsprimarystructure.Everyproteinalsowinds,coils,andfoldsinthree-dimensionalspaceinspecificandpredeterminedways,takingonauniquesecondary(initialwindingandcoiling)andtertiarystructure(overallfolding).Inharshconditions,suchashightemperatureorextremepH,proteinscanlosetheirnormaltertiaryshapeandceasetofunctionproperly.Whenaproteinunfoldsinharshconditions,ithasbeen“denatured.”血脂相連。這種鏈不溶于水，由于他們非極性。甘油三酯甘油三酸酯的構成為三條長鏈烴末端連有不飽和脂肪酸，叫做甘油。由于他們包括3個脂肪酸，脂肪油砂也被稱為甘油三酯。由于這點，甘油和脂肪酸，相互進入對方脫水的合成。肪酸的油脂。飽和脂肪沒有碳碳雙鍵，不飽和脂肪酸，而包含一個或多個這樣碳碳雙鍵。在和脂肪通常是液體。LipidsLipidsarecarboncompoundsthatdonotdiss