2013年职称英语备考每日练习理工类20

考试站网校职称英语频道首发，为了帮助学员备考2013年职称外语考试，特别整理了职称英语考试理工类:阅读理解资料，供大家复习备考之用，希望大家顺利通过考试！　 阅读下面的短文。每篇短文的后面有五个问题，每个问题有四个备选答案。请根据短文的内容选择最佳答案。每个试题计3分,共计15分
　　 Sugar Power for Cell Phones
　　 Using enzymes commonly found in living cells，a new type of fuel cell produces small amounts of electricity from sugar．If the technology is able to succeed in mass production，you may some day share your sweet drinks with your cell phone．
　　 In fuel cells，chemical reactions generate electrical currents．The process usually relies on precious metals，such as platinum．In living cells，enzymes perform a similar job，breaking down sugars to obtain electrons and produce energy．考试站网
　　 When researchers previously used enzymes in fuel cells，they had trouble keeping them active，says Shelley D．Minteer of St Louis University1．Whereas biological cells continually produce fresh enzymes，there’s no mechanism in fuel cells to replace enzymes as they quickly degrade．
　　 Minteer and Tamara Klotzbach，also of St Louis University，have now developed polymers that wrap around an enzyme and preserve it in a microscopic pocket．“We tailor these pockets to provide the ideal microenvironment” for the enzyme，Minteer says．The polymers keep the enzyme active for months instead of days．
　　 In the new fuel Cell，tiny polymer bags of enzyme are embedded in a membrane that coats one of the electrodes．When glucose from a sugary liquid gets into a pocket，the enzyme oxidizes it，releasing electrons and protons．The electrons cross the membrane and enter a wire through which they travel to the other electrode，where they react with．oxygen in the atmosphere to produce water．The flow of electrons through the wire constitutes an electrical current that can generate power．
　　 So far，the new fuel cells don’t produce much power，but the fact that they work at all is exciting，says Paul Kenis，a chemical engineer at the University of Illinois2 at Urhana-Champaign3．“Just getting it to work．” Kenis says，“is a major accomplishment．”