问题 单项选择题

头孢他啶抗菌作用的机制是影响()

A.细胞壁的合成

B.细胞膜的合成

C.营养物质的输送

D.蛋白质的合成

E.核酸的复制

答案

参考答案:A

解析:头孢他啶抗菌作用机制为与细菌细胞膜上的青霉素结合蛋白(PBPs)结合,使转肽酶酰化,抑制细菌中隔和细胞壁的合成,影响细胞壁黏肽成分的交叉连结,使细胞分裂和生长受到抑制,细菌形态变长,最后溶解和死亡。

阅读理解

阅读理解

       Over the last 70 years, researchers have been studying happy and unhappy people and finally found

out ten factors that make a difference. Our feelings of well-being at any moment are decided to a certain

degree by genes. However, of all the factors, wealth and age are the top two.

       Money can buy a degree of happiness. But once you can afford to feed, clothe and house yourself,

each extra dollar makes less and less difference.

       Researchers find that, on average, wealthier people are happier. But the link between money and

happiness is complex(复杂的). In the past half-century, the average income (平均收入) has sharply

increased in developed countries, yet happiness levels have remained almost the same. Once your basic

needs are met, money only seems to increase happiness if you have more than your friends, neighbors and colleagues.

       "Dollars buy status (social position), and status makes people feel better," say some experts, which

helps explain why people who can seek status in other ways, scientists or actors, for example, may happily accept relatively poorly-paid jobs.

       In a research, Professor Alex Michalos found that the people whose desires (欲望), not just for

money, but for friends, family, job, health, rose furthest beyond what they already had, tended to be less

happy than those who felt a smaller gap (差距). Indeed, the size of the gap predicted happiness about

five times better than income alone. "The gap measures just blow away the measures of only income."

says Michalos.

       Another factor that has to do with happiness is age. Old age may not be so bad "Given all the

problems of aging, how could the elderly be more satisfied?" asks Professor Laura Carstensen. In one

survey, Carstensen interviewed 184 people between the ages of 18 and 94, and asked them to fill out an

emotion questionnaire. She found that old people reported positive emotions just as often as young people. Some scientists suggest older people may expect life to be harder and learn to live with it, or they're more

realistic about their time running out. Older people have learned to focus on things that make them happy

and let go of those that don't.

       "People realize not only what they have, but also that what they have cannot last forever," she says.

"A goodbye kiss to a husband or wife at the age of 85, for example, may bring far more complex emotional responses than a similar kiss to a boy or girl friend at the age of 20."

1. Some actors would like to accept poorly-paid jobs because the jobs____ .

A. make them feel much better

B. provide chances to make friends

C. improve their social position

D. satisfy their professional interests

2. Professor Alex Michalos found that people feel less happy if _____.

A. the gap between reality and desire is bigger

B. they have a stronger desire for friendship

C. the hope for good health is much greater

D. their income is far below their expectation

3. We can infer from the passage that older people _____.

A. would like to have more goodbye kisses than young people

B. are used to living a hard life because they are kind to others

C. express their positive opinions just as some young people do

D. find it easier to feel happy because they are more realistic

4. According to the passage, the feeling of happiness _____.

A. increases gradually with age

B. is controlled partly by desires

C. has little to do with wealth

D. is decided mostly by genes

单项选择题 A1型题