7．正常精细胞形成精子的过程中，细胞的很多结构退化消失，但保留了大量线粒体，因为线粒体可以合成精子运动所需的
A．乙醇 B．ATP C．胰岛素 D．淀粉
6．黄曲霉毒素是毒性极强的致癌物质，有关研究发现，它能引起细胞中的核糖体不断从内质网上脱落下来，这一结果直接导致
A．核仁被破坏 B．染色体被破坏 C．细胞膜被破坏 D．蛋白质合成受到影响
5．下列有关生物体遗传物质的叙述，正确的是
A．豌豆的遗传物质主要是DNA B．酵母菌的遗传物质主要分布在染色体上
C．T2噬菌体的遗传物质含有硫元素 D．HIV的遗传物质水解产生4种脱氧核苷酸
4．下列关于细胞内化合物的叙述，正确的是
A．ATP脱去2个磷酸基团后是RNA的基本组成单位之一 B．糖原代谢的最终产物是葡萄糖
C．蔗糖和乳糖水解的产物都是葡萄糖 D．脂肪和生长激素是生物体内的能源物质
3．下列关于组成细胞化合物的叙述，不正确的是
A．蛋白质肽链的盘曲和折叠被解开时，其特定功能并未发生改变
B．RNA与DNA分别由四种核苷酸组成，可以储存遗传信息
C．DNA分子碱基的特定排列顺序，构成了DNA分子的特异性
D．胆固醇是构成细胞膜的重要成分，在人体内参与血液中脂质的运输
2．施莱登和施旺共同提出
A．细胞学说 B．分离定律 C．进化学说 D．中心法则
1．右图所示的细胞可能是
A．酵母菌细胞 B．原核细胞 C．动物细胞 D．植物细胞
8.(★★★★★)The passage mainly suggests that ________.
A.now men pay more attention to their clothes than women do
B.women always like beautiful dresses
C.people have paid more and more attention to the importance of dress
D.American culture is changing greatly
7.(★★★★★)It can be inferred from the passage that the author was ________.
A.a scientist as well as a naturalist B.a naturalist as well as a scientist
C.no more than a born naturalist D.first of all a scientist
H
There is probably no field of human activity in which our values and lifestyles are shown more clearly and strongly than they are in the clothes that we choose to wear.The dress of an individual is a kind of “sign language ” that communicates a set of information and is usually the basis on which immediate impressions are formed.Traditionally,a concern for clothes was considered to be an affair of females,while men took pride in the fact that they were completely lacking in clothes consciousness(意识).
This type of American culture is by degrees changing as man dress takes on greater variety and color.Even as early as 1955,a researcher in Michigan said that men attached rather high importance to the value of clothing in daily life.White-collar- workers in particular viewed dress as a symbol(象征) of ability,which could be used to impress or influence others,especially in the work situation.The white-collar worker was described as extremely concerned about the impression his clothing made on his superiors(上司).Although blue-collar workers were less aware(察觉到的) that they might be judged on the basis of their clothing,they recognized that any difference from the accepted pattern of dress would be made fun of by fellow workers.
Since that time,of course,the patterns have changed:the typical office worker may now be wearing the blue shirt,and the laborer a white shirt;but the importance of dress has not become less.Other researchers in recent years have helped to prove its importance in the lives of individuals at various age levels and in different social and economic status groups(阶层).
6.(★★★★★)You may find this passage in ________.
A.a newspaper B.a book
C.a magazine D.an official document
G
Looking back on my childhood,I realize that naturalists are born and not made.Although we were all brought up in the same way,my brothers and sisters soon gave up their pressed flowers and insects.Unlike them,I had no ear for music and languages.I was not an early reader and I could not do mental arithmetic.
Before World War Ⅰ we spent our summer holidays in Hungary.I have only the unclear memory of the house we lived in,of my room and my toys .Nor do I recall clearly the large family of grandparents,aunts,uncles and cousins who gathered next door. But I do have a clear memory of the dogs,the farm animals,the local birds,and above all,the insects.
I am a naturalist,not a scientist.I have a strong love of the natural world and my eagerness has led me into varied studies or research.I love discussing my favorite topics and enjoy burning the midnight oil while reading about other people’s observations and discoveries.Then something happens that brings these observations together in my sensible mind.Suddenly you imagine you see the answer to the puzzling question,because it all seems to fit together.This has resulted in my publishing 300 papers and books,which some might honor with the title of scientific research.
But curiously,a sharp eye,a good memory and enjoyment of the animal and plant worlds do not make a scientist;one of the best-known and important qualities required is self-training,a quality I lack.A scientist requires not only self-discipline but hard training,determination and a goal.A scientist,up to a point,can be made.A naturalist is born.If you can combine the two,you get the best of both.