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单选题

A．It divides into two different parts.
B．It keeps the same chemical structure.
C．It becomes part of a new chemical compound.
D．It produces more of the enzyme (酶).

参考答案B

解析:Let' s begin today by discussing enzymes. Enzymes are what make many of the body' s biochemical reactions possible. Actually biochemical reactions can take place without them, but at much lower rates. In fact an enzyrnc may cause a reaction to proceed billions of times faster than it would otherwise. Before I go on to the biochemical specifics of how this works, let mc provide a figurative example. I think it will help illustrate the power of enzymes more clearly. Now, suppose you got a bag and you put a bunch of locks in it. Then you put in all the keys that go with the locks. And you closed the bag and shook it hard. No matter how long you shook, chances arc very small that any key would get inserted in any of the locks. But if you took them all out of the bag and this time used your hands to insert the keys in the locks, you could combine them much quicker.Enzymes act like your hands, quickly allowing chemical reactions that would otherwise take much longer. Now, there arc two reasons that enzymes are so effective at enabling biochemical reactions.
First enzymes greatly reduce the amount of energy required to start the reactions, and with less energy nccdcd the reactions can proceed a lot faster than they could without the enzyme. The second reason is that on a small amount of an enzyme is nccdcd to enable the biochemical reaction. That's because the chemical structure of the enzyme itself does not become altered as if enables the reaction. So a single enzyme can be used to start the same biochemical reaction over and over again.
解析
What point does the professor make about an enzyme when it is involved in a biochemical reaction?
细节题。根据讲座内容及结尾的That’s because the chemical structure of the enzyme itself does not become altered as if enables the reaction．So a single enzyme Can be used to start the same biochemical reaction over and over again．可知，教授指出酶在生化反应中保持不变的化学结构。因此。正确答案为B。

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A．Provide extra energy to start the reaction.
B．Raise the temperature of the chemicals.
C．Release a chemical needed to start the reaction.
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单选题

A．To show that enzymes are very effective.
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D．To describe different types of enzymes.

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