资源描述：
《考研英语阅读模拟试题及答案01》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。
1、Ithaslongbeenknownthattherateofoxidativemetabolism(theprocessthatusesoxygentoconvertfoodintoenergy)inanyanimalhasaprofoundeffectonitslivingpatterns.Thehighmetabolicrateofsmallanimals,forexampletgivesthemsustainedpowerandactivityperunitofweight,butatthec
2、ostofrequiringconstantconsumptionoffoodandwnte匚Verylargeanimals,withtheirrelativelylowmetabolicratescansurvivewellonasporadicfoodsupply,butcangen-eratelittlemetabolicenergypergramofbodyweight.Ifonlyoxidativemetabolicniteisconsidered,there-fore,onemighta
3、ssumethatsmaller,moreactive,animalscouldpreyonlargerones,atleastiftheyattackedingroups・Perhapstheycouldifitwerenotforanaerobicglycolysis,thegreatequalize匚Anaerobicglcolysisisaprocessinwhichenergyisproduced,withoutoxygen,throughthebreakdownofmuscleglycog
4、enintolacticacidandadenosinetri-phosphate(ATP),theenergyprovider.Theamountofenergythatcanbeproducedanaerobicallyisafunctionoftheamountofglycogenpresent-inallvertebratesabout0.5percentoftheirmuscles1wetweight.Thustheanaerobicenergyreservesofaverte-bratea
5、reproportionaltothesizeoftheanimal.If,forexample,somepredatorshadattackeda100-tondinosaur,nonnallytorpid，thedinosaurwouldhavebeenabletogeneratealmostinstantaneously»viaanaerobicglycolysis,theenergyof3,000humansatmaximumoxidativemetabolicenergyproduction
6、.Thisexplainshowmanylargespecieshavemanagedtocompetewiththeirmoreactiveneighbors：thecompensationforalowoxidativemetabolicrateisglycolysis.Therearelimitations,however,tothiscompensa-tion.Theglycogenreservesofanyanimalaregood,atmost,foronlyabouttwominutes
7、atmaximumeffort,afterwhichonlythenormaloxidativemetabolicsourceofenergyremains.Withtheconclusionofaburstofactivitythelacticacidlevelishighintthebodyfluids,leavingthelargeanimalvulnerabletoattackuntiltheacidisreconverted,viaoxidativemetabolism,bytheliver
8、intoglucose,whichisthensent(inpart)backtothemusclesforglycogenresyn-thesis.Duringthisprocesstheenormousenergydebtthattheanimalhasrunupthroughanaerobicglycolysismustberepaid,adebtthatisproportionallymuchgreaterforthelargervertebra
