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托福TPO-26 Lecture 3(上)

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Listen to part of a lecture in a biology class.

听一段生物课。

OK, just before the end of the last class, we started talking about trace metals, metals found in living organisms in very small quantities that serve an important biological and important nutritive function in those organisms.

好了,就在上节课结束前, 我们开始讲微量金属,即在生物体中含量非常低的金属元素,对生物体而言具有很重要的生物和营养功能。

And one trace mental that serves a nutritive function is zinc.

一种具有营养功能的微量金属是锌。

Zinc assists in a number of processes in humans, but we are going to focus on just one, one that applies to a number of organisms, not just humans.

锌在人体内协助很多生物进程的进行,但今天我们主要关注于一种进程,不仅仅适用于人类,也适用于很多其它生物体。

See, zinc plays a major role in carbon cycling, the conversion of various kinds of molecules with carbon, like carbon dioxide into other kinds of molecules with carbon that organisms can use.

锌在碳循环中起重要作用,即不同的含碳分子之间的转换,像是二氧化碳转变成其它种类的含碳分子,可供生物体利用。

So, take respiration, our bodies---our cells produce carbon dioxide when they break down sugars.

拿呼吸作用举例,我们的身体——我们的细胞在分解糖分时会产生二氧化碳。

We need to get CO2 out of our bodies, so the CO2 is converted into carbonic acid, which the blood is able to carry to the lungs.

我们要把二氧化碳排出体外,所以二氧化碳被转成了碳酸,这样血液就能将其运输至肺部。

Once the carbonic acid reaches the lungs, it's converted back into carbon dioxide, so that we can breathe it out.

一旦碳酸到达肺部,就会重新转变成二氧化碳,然后我们就能通过呼吸排出。

Now, this whole conversion process relies on a particular enzyme.

整个转变过程依靠一种特定的酶。

Um, who remembers what an enzyme is? Bob?

谁记得这种酶是什么?鲍勃?

Um, it's a protein, a specific kind of protein, one that speeds up chemical reactions.

这是一种蛋白质,一种特定的蛋白质,能加快化学反应。

Exactly, different enzyme assists in different chemical reactions.

正确,不同的酶能辅助不同的化学反应。

Now, the one that speeds up the conversion of carbon dioxide has zinc in it.

那种能加快二氧化碳转化的酶含有锌。

So this zinc enzyme is critical for getting CO2 out of our bodies through the lungs.

所以,要把二氧化碳由肺部排出我们体外,这种含锌酶至关重要。

And it's also extremely important for plants.

同时它对植物也非常重要。

Bob, can you tell us why?

鲍勃,你能告诉我们这是为什么吗?

For making food, for photosynthesis?

为了制造养分,为了光合作用?

Exactly! For photosynthesis.

完全正确!就是为了光合作用。

Plants also convert carbon dioxide into different forms of carbon-containing molecules and the conversion process used relies on the very same enzyme that works in humans.

植物也会将二氧化碳转化为其它含碳分子,其涉及的转化过程中也依靠于这种酶,和在人体中起作用的酶一样。

So, zinc is also important for plants.

所以,锌对植物来说也很重要。

OK, but zinc is scarce in certain environments, and it is particularly scarce in waters near the surface of rivers and lakes and shallower parts of oceans, which might make us wonder how plants could live there at all.

好了,但锌在一些环境中很稀少,特别是在接近水面的河水和湖水里,还有较浅的海水里,这不禁让我们感到疑惑,在那儿的植物是怎么活下来的。

In fact, there are a lot of marine plants that survive, that grow and reproduce in surface waters.

事实上,有很多海洋植物生存下来了,在表层水里茁壮成长,不断繁殖。

In particular, there are a lot of diatoms.

那里特别多硅藻。

重点单词   查看全部解释    
extremely [iks'tri:mli]

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adv. 极其,非常

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trace [treis]

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n. 痕迹,踪迹,微量
vt. 追踪,找出根源

 
conversion [kən'və:ʃən]

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n. 转变,改变信仰,换位

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convert ['kɔnvə:t,kən'və:t]

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v. 变换,(使)转变,使 ... 改变信仰,倒置,兑换

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survive [sə'vaiv]

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vt. 比 ... 活得长,幸免于难,艰难度过

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produce [prə'dju:s]

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n. 产品,农作物
vt. 生产,提出,引起,

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scarce [skɛəs]

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adj. 缺乏的,不足的,稀少的,罕见的
ad

 
photosynthesis [.fəutəu'sinθəsis]

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n. 光合作用

 
reproduce [.ri:prə'dju:s]

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v. 再生,复制,生殖

 
protein ['prəuti:n]

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n. 蛋白质

 


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