问题 问答题 简答题

从某种培养细胞中分离出5个突变体,它们的生长都需要G化合物。已知细胞内几种化合物A、B、C、D、E的生物合成途径,并如下表测试了这几种化合物能否支持每种突变体(1~5)生长:

试问:(a)A、B、C、D、E、G六种化合物在生物合成途径中的先后次序是什么

(b)每种突变体在这一生物合成途径的哪一点发生阻断

答案

参考答案:

(a)6种化合物在生物合成途径中的先后次序是E→A→C→B→D→G

(b)每种突变体在这一生物合成途径中发生阻断的位置分别为: 5 4 2 1 3 E→A→C→B→D→G

阅读理解

The days are getting shorter and shorter, and temperatures are dropping. Winter is coming and it is easy for people to catch flu. Many people have started taking vitamin C pills as a precautionary(预防的)way. But a research has shown that vitamin C pills do not provide as much protection as they think. They are even not as good as other ways, like often washing your hands. Some German scientists have given people information and a test on the subject helping to stop incorrect ways.

Whether it is caused by cold or flu(流行性感冒), a runny nose and sore throat are signs of catching a cold. Many people overestimate(高估) the advantages of vitamin C and other pills. For years it was believed that taking vitamin C pills not only provided protection against colds but also against cancers, helping people to live longer. But the result of the research showed disagreement on these beliefs(看法). The result has now come out on the website wwww.informedhealthonline.org. “Some pills may not help people live longer. Some pills may even lead to earlier death,” says Professor Peter Sawicki. Scientists also say that the best way to get vitamins is through food instead of having vitamin pills. That is to say, we disagree with the way of taking vitamin C pills.

There are many simple but useful ways to lower the risk of catching a cold. These include often washing your hands with normal soap(肥皂) and water and not touching your face with your hands. People who have already had a cold can stop it from spreading by throwing away tissues(纸巾) at once after using them and not shaking hands with other people.

小题1:Most people believe that taking vitamin C pills can _______.

A.make them catch a cold easily

B.provide protection against colds

C.make them cleverer

D.prevent all illnesses小题2:A runny nose and sore throat mean someone ________.

A.will catch a cold in a few days

B.would never catch a cold

C.has caught a cold

D.would never spread colds to others小题3:The best way to get vitamins is _______.

A.eating food which contains Vitamins

B.taking vitamin pills

C.drinking water which contains vitamins

D.eating as much pork as possible小题4:_______ is NOT an effective way to lower the risk of catching a cold.

A.Not touching your face with your hands

B.Often washing your hands with normal soap and water

C.Not shaking hands with those people who have already had a cold

D.Not throwing away tissues at once after using them小题5:About taking vitamin C pills, _______ is shown by the research.

A.fighting against sore throat

B.fighting against colds and cancers

C.helping people live longer

D.leading to earlier death by some pills

问答题