Official 39 Set 6

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
置顶

Potential Energy Source - Cellulose

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
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

显示答案 正确答案: D

我的笔记 编辑笔记

/
  • 原文
  • 译文
  • 查看听力原文

    关闭显示原文

    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.

  • 旁白:请听一段生物学讲座的节选片段。

    教授:大家今天的阅读材料是关于潜在的替代能源。今天我要做的事情之一就是来讨论其中一种潜在的能源:纤维素。谁可以告诉我纤维素是什么?Alan?

    学生:纤维素。是的。这是一种由简单糖类构成的坚硬的有机分子。它被发现在所有的植物细胞的细胞壁中,在青草,树木,所有的植物,在地球上,纤维素是最多的有机粒子。

    教授:好的。在某种程度上纤维素也是一种大量的潜在能源,部分原因是它在自然界里储量丰富。很多有机体靠消化纤维素产生的能量而生存,就像是很多种类的细菌或者母牛和山羊一样。母牛和山羊进化出了高度特殊化的消化系统,这个消化系统可以让它们消化掉纤维素。

    学生:但是对于大多数物种而言,加工处理纤维素是困难的?

    教授:是的。而且研发出一种可控的方式,在实验室里加工处理纤维素,让我们使用储存在其中的能量是很难的。纤维素需要先被转化成乙醇。让我解释一下,乙醇是液体,一种酒精,这种物质来自于从植物中产生糖的过程,原料一般是玉米,乙醇还可以被用作燃料。很多研究者相信,纤维素可以终结人类对于汽油的依赖。问题是我们现在以玉米为原料产生的乙醇中获得的能量并不比投入生产它上面的能量多,所以并不是很值得,Tina?

    学生:但是从纤维素中制造的乙醇不一样?

    教授:是的。产自纤维素的或者纤维素类乙醇的能量,可能质量更好。

    学生:好吧。所以为什么我们不直接使用纤维素乙醇呢?

    教授:问题就是,现在的把纤维素加工成乙醇的技术还很贵,而且不能大批量转化。目前,现在这个转化过程主要有两个关键步骤。第一步是把纤维素分解成糖类。这需要通过酶来完成,酶是一种特殊的蛋白质。第二点,在酶把纤维素分解了之后,酵母和其他的微生物、细菌等会被加入,来发酵这些糖类,最后生成纤维素乙醇。

    问题是,我们在生产这些分解纤维素的酶的时候并没有很成功。这些蛋白质很难生产,即使是在实验室里,所以通常来说我们会在产生它们的微生物里直接提取这种酶。不幸的是,这个过程很慢,很贵,而且效率不高。

    学生:所以科学家正在努力研发一种生产酶的更好的办法?

    教授:实际上有一家公司觉得他们可以做的更好。把这两个步骤合二为一,可以更高效,更经济。意思是,我们可以找到一种有机物,既可以分解纤维素也可以把它转化成乙醇。所以这家公司做的是在全世界寻找并收集这种自然界产生的有机物。我的意思是,开发纤维素所含能量的关键可能藏在某个丛林里的特殊种类的细菌或者酵母身上。

    所以这个公司的研究人员已经发现了一些微生物,这些微生物可以把纤维素转化为乙醇。现在他们正忙于加强、改进这些微生物的某种自然特征,通过某种复杂的科技操纵它们,来让它们转化得更有效率。这个目标现在看来已经近在咫尺,设计及建造一个超级病菌,一个特定种类的微生物,这个微生物可以使得对于纤维素乙醇的便宜经济的转化变成可能。

  • 官方解析
  • 网友贡献解析
  • 本题对应音频:
    0 感谢 不懂
    音频1
    解析

    题型分类:主旨题

    音频定位:

    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.

    选项分析:

    听到today要仔细听了,教授讲今天要讲一种潜在的能源来源——纤维素。结合后文我们知道纤维素有巨大的生成乙醇的潜力。

    标签

题目讨论

如果对题目有疑问,欢迎来提出你的问题,热心的小伙伴会帮你解答。

如何吃透这篇文章?

Potential Energy Source - Cellulose

0人精听过

预计练习时间:15min20s

马上精听本文

最新提问