试题与答案

以Na+-K+泵为例，说明物质的主动运输过程。

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题型：问答题 简答题

题目：

以Na+-K+泵为例，说明物质的主动运输过程。

答案：

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参考答案：Hatch

考点：生物学生物物理学生物物理学题库
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题型：阅读理解

阅读理解。

      When people lose legs after accidents or illnesses, emergency care and artificial limbs(假肢)

often allow them to walk again. Newts (蝾螈)in the same situation, on the other hand, can grow

limbs back on their own! Scientists have known for a long time that certain animals can regrow

limbs, but they haven't quite figured out how these creatures do it.

     Researchers have now come up with some new ideas. Their work may give people the ability

to regrow lost limbs.  The researchers started with two simple experiments: when you cut a newt's

 leg at the ankle, only the foot grows back; when you cut off a leg at the very end, the whole leg

grows back.  In both cases, the regrowth begins with stem cells.  Stem cells can develop into nearly

any type of cell in the body.

     How do a newt's stem cells know when to grow only a foot and when to regrow a whole leg?

     This question relates to another mystery. In newt's, a cutoff leg will grow back only if the nerve

bundle(神经束) in it also grows back, but if something prevents the nerve bundle from growing the

stem cells at the wound won't  regrow a new leg.

     In its study, a British team focused on a protein called nAG.  When the team prevented nerves in

a limb from growing, but added the nAG protein to stem cells in the limb, the limb still regrew. That

protein seems to guide limb regrowth. People have proteins that are similar to nAG.  Further research

into these materials may someday help human limbs recover by themselves.

1. A newt will regrow its leg if________.

A. its ankle was cut off but the nerve bundle was good

B. its leg was cut off and the nerve bundle stopped growing

C. its leg was cut off and the nerve bundle could grow back

D. its ankle and the nerve bundle could grow back

2. What do the underlined words "these materials"  refer to?

A. Nerve bundles and proteins.  

B. Proteins similar to nAG.

C. Stem cells and proteins.  

D. Stem cells and nerve bundles.

3. The first sentence of the passage________.

A. acts as a leadin

B. shows where researchers got their new ideas

C. states the author's opinion

D. describes the result of researchers' studies

4. What's the purpose of studying the newts?

A. To find out whether newts would regrow after being cutting off.

B. To find out the similarity between human and newts.

C. To find out what is nAG.

D. To find a way of helping human limbs recover by themselves.
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题型：阅读理解

"Indeed," George Washington wrote in his diary in 1785, "some kind of fly, or bug, had begun to eat the leaves before I left home." But the father of America was not the father of bug. When Washington wrote that, Englishmen hade been referring to insects as bugs for more than a century, and Americans had already created lightning-bug(萤火虫). But the English were soon to stop using the bugs in their language, leaving it to the Americans to call a bug a bug in the nineteenth and twentieth centuries.

　　The American bug could also be a person, referring to someone who was crazy about a particular activity. Although fan became the usual term, sports fans used to be called racing bugs, baseball bugs, and the like.

　　Or the bug could be a small machine or object, for example, a bug-shaped car. The bug could also be a burglar alarm, from which comes the expression to bug, that is, "to install (安装) an alarm". Now it means a small piece of equipment that people use for listening secretly to others' conversation. Since the 1840s, to bug has long meant "to cheat", and since the 1940s it has been annoying.

　　We also know the bug as a flaw in a computer program or other design. That meaning dates back to the time of Thomas Edison. In 1878 he explained bugs as "little problems and difficulties" that required months of study and labor to overcome in developing a successful product. In 1889 it was recorded that Edison "had been up the two previous nights discovering 'a bug' in his invented record player."

小题1:We learn from Paragraph 1 that __________________.

A．Americans had difficulty in learning to use the word bug

B．George Washington was the first person to call an insect a bug

C．the word bug was still popularly used in English in the nineteenth century

D．both Englishman and Americans used the word bug in the eighteenth century小题2:What does the word "flaw" in the last paragraph probably mean?

A．Fault.

B．Finding.

C．Origin.

D．Explanation.小题3:The passage is mainly concerned with__________________.

A．the misunderstanding of the word bug

B．the development of the word bug

C．the public views of the word bug

D．the special characteristics of the word bug
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