400-820-0859Potential Alternative Source of Energy-cellulose托福听力原文翻译及问题答案
一、Potential Alternative Source of Energy-cellulose托福听力原文：
NARRATOR:Listen to part of a lecture in a biology class.
FEMALE PROFESSOR:Your reading for today's class was about potential alternative sources of energy.So one thing I want to do today is consider one of those potential energy sources,cellulose.
Who can tell us what cellulose is?Allen?
MALE STUDENT:Cellulose,yeah,it's a tough organic molecule…made of simple sugars.It's found in the walls of all plant cells…in grass,trees…all plants,and,well…there's more cellulose than any other organic molecule on Earth.
FEMALE PROFESSOR:Good.It's also a potential tremendous source of energy,in part because there's so much of it.
Now,many organisms live on the energy they derive from consuming cellulose—like many species of bacteria…or cows and goats.Cows and goats have evolved highly specialized digestive systems that allow them to metabolize cellulose.
MALE STUDENT:But it's hard for most species to process cellulose?
FEMALE PROFESSOR:Yes,and it's been very hard to develop a controlled way to process cellulose in a lab,so that we can use the energy that's stored in it.It needs to be converted into ethanol.
Let me explain….Ethanol is a liquid,a kind of alcohol that is derived from processing sugars from plants,often corn,and it can be used as fuel.Many researchers believe it is the key to ending the reliance on gasoline.
The problem is that the amount of energy we get from corn-based ethanol isn't much more than the amount of energy that gets put into making it,so it's not really worth it.Tina?
FEMALE STUDENT:But ethanol made from cellulose is different?
FEMALE PROFESSOR:Yes—it's possible to get a vastly better energy yield on cellulose-based,or cellulosic,ethanol.
FEMALE STUDENT:OK,so why don't we just use cellulosic ethanol?
FEMALE PROFESSOR:Well,the problem is that the current method for processing cellulose into ethanol is very expensive and can't be done on a large scale.
See,currently,there are two key steps in the process.
The first is breaking the cellulose down into sugars.This is done with an enzyme,a specific type of protein.And second,after the enzyme has broken down the cellulose,yeast and other microorganisms—microbes—are added to ferment those sugars into cellulosic ethanol.
Thing is,though,we're not too good at producing the enzymes that break down cellulose.Those proteins are very difficult to make,to just assemble in a lab,so usually we extract enzymes from microorganisms that produce them naturally.Unfortunately,this is slow,expensive,and just not very efficient
MALE STUDENT:So are they trying to develop a better way to make enzymes?
FEMALE PROFESSOR:Actually,there's a company that thinks they can do better than that.It'd be more efficient,and therefore cheaper,to combine the two steps I mentioned into one.That is,have a single organism that breaks down cellulose and then produces ethanol.So,what this company is doing is searching around the world and gathering naturally occurring microorganisms that do both things.
I mean,the best key to unlocking the power of cellulose may well lie in a rare species of bacteria or yeast in a jungle somewhere.
So,researchers at this company have discovered some microorganisms that process cellulose and produce ethanol.Now,they’re working on enhancing,improving,certain natural characteristics of these microorganisms…manipulating them with sophisticated technology…to make them work even more efficiently.The goal,which seems to definitely be within reach,is to design and engineer a superbug,a specific kind of microbe,that makes cheap,commercial production of cellulosic ethanol a real possibility.
二、Potential Alternative Source of Energy-cellulose托福听力中文翻译：
旁白：在生物课上听一节课的一部分。
女教授：你今天课上读的是关于潜在的替代能源。所以我今天想做的一件事就是考虑一种潜在的能源，纤维素。
谁能告诉我们纤维素是什么？艾伦？
男生：纤维素，是的，它是一种坚硬的有机分子……由单糖组成。它存在于所有植物细胞的壁中……在草、树……所有植物中……而且，嗯……纤维素比地球上任何其他有机分子都多。
女教授：好。它也是一种潜在的巨大能源，部分原因是它的储量太大了。
现在，许多生物体像许多细菌物种或奶牛和山羊一样，依靠消耗纤维素产生的能量生存。奶牛和山羊已经进化出高度专业化的消化系统，使它们能够代谢纤维素。
男学生：但大多数物种很难加工纤维素？
女教授：是的，很难在实验室里开发出一种可控的纤维素加工方法，这样我们就可以利用其中储存的能量。它需要转化为乙醇。
让我解释一下…。乙醇是一种液体，是一种从植物（通常是玉米）加工糖中提取的乙醇，可以用作燃料。许多研究人员认为，这是结束对汽油依赖的关键。
问题是，我们从玉米乙醇中获得的能量并不比制造乙醇所需的能量多多少，所以这并不值得。蒂娜？
女学生：但是由纤维素制成的乙醇是不同的？
女教授：是的，基于纤维素或纤维素的乙醇有可能获得更好的能源产量。
女生：好吧，那我们为什么不直接用纤维素乙醇呢？
女教授：问题是，目前将纤维素加工成乙醇的方法非常昂贵，无法大规模进行。
请参阅，目前，该过程有两个关键步骤。
首先是将纤维素分解成糖。这是用一种特定类型的蛋白质酶来完成的。其次，在酶分解纤维素后，添加酵母和其他微生物，将这些糖发酵成纤维素乙醇。
但问题是，我们不太擅长产生分解纤维素的酶。这些蛋白质很难制造，很难在实验室组装，所以我们通常从自然产生它们的微生物中提取酶。不幸的是，这样做速度慢、成本高，而且效率不高
男学生：那么他们是不是在尝试开发一种更好的酶的制造方法？
女教授：事实上，有一家公司认为他们可以做得更好。将我提到的两个步骤合并为一个步骤会更有效，因此***。也就是说，只有一种有机体能分解纤维素，然后产生乙醇。所以，这家公司正在全球范围内进行搜索，并收集自然产生的微生物，这两种微生物都起作用。
我的意思是，释放纤维素能量的最佳钥匙可能就在某个丛林中的稀有细菌或酵母物种中。
因此，该公司的研究人员发现了一些加工纤维素和生产乙醇的微生物。现在，他们正致力于增强、改善这些微生物的某些自然特性……用尖端技术操纵它们……使它们更有效地工作。这一目标似乎很容易实现，即设计和制造一种超级细菌，一种特殊的微生物，使纤维素乙醇的廉价商业化生产成为可能。
三、Potential Alternative Source of Energy-cellulose托福听力问题：
Q1:1.What is the discussion mainly about?
A.Advantages of cellulose over traditional sources of fuel.
B.A recent study about microorganisms that process cellulose.
C.Some newly discovered characteristics of cellulose.
D.Challenges involved in converting cellulose into fuel.
Q2:2.According to the speakers,why is cellulose such a significant potential source of energy?
A.Because it is so abundant in nature.
B.Because it is so easily created in a lab.
C.Because its enzymes have so many uses.
D.Because it can be processed in just a few steps.
Q3:3.What is the professor's opinion about corn-based ethanol?
A.She thinks using it in motor vehicles may harm the environment.
B.She thinks it is not an energy-efficient alternative to gasoline.
C.She thinks it will eventually become cheaper to produce.
D.She thinks researchers should invest more in its development.
Q4:4.The professor describes the current method for producing cellulose ethanol.What are the two important steps she mentions?[Click on 2 answers.]
A.Yeast is added to cellulose to create an enzyme.
B.An enzyme breaks down cellulose into sugars.
C.Microorganisms ferment sugars into alcohol.
D.Ethanol is extracted from certain microorganisms.
Q5:5.What does the professor imply about a superbug?[Click on 2 answers.]
A.It will be an altered version of a naturally occurring organism.
B.It was discovered as a result of looking for new sources of cellulose.
C.It may contribute to the development of an efficient way to produce ethanol
D.It may produce many kinds of alternative fuels.
Q6:6.Why does the professor says this:
A.To emphasize the necessity of working to preserve rare species.
B.To suggest that the company will never find what it is looking for.
C.To emphasize that bacteria that break down cellulose are too rare to be useful.
D.To indicate that she endorses the company's strategy.
四、Potential Alternative Source of Energy-cellulose托福听力答案：
A1:正确答案：D
A2:正确答案：A
A3:正确答案：B
A4:正确答案：BC
A5:正确答案：AC
A6:正确答案：D
