问题 问答题 简答题

为什么DNA不易被水解,而RNA易被水解?

答案

参考答案:

因为RNA的核糖上多了一个2’-OH,2’-OH在碱的作用下形成磷酸三脂,磷酸三脂极不稳定,立即水解形成2’,3’-环磷酸脂,再在碱的作用下形成水解产物2’-核苷酸,3’-核苷酸,但是DNA的脱氧核糖没有活泼的-OH,因此在碱性条件下不受影响

阅读理解与欣赏

阅读下面文章,完成以下题目

天坛之美

始建于明永乐十八年的天坛,是世界建筑艺术的珍品。它具有一种独特的意境,它以教练的艺术形成式表现了埔大深遂的精神内涵,体现了中国古人对宇宙的思考和想象。

天坛的意境美,可以归纳为:高 圆 清。

“高”是天的一种特性。天坛的建筑是连续性的逐渐上升的完整体,从南北中轴线上看,南端的圈丘高5.18米,皇穹宇高19.2米,诉外殿上升到38米,成为中轴线的高峰。故宫太和殿是永乐以前全城最高的建筑,是帝王的象征,而扩年殿比大和殿还高出3米,成为天帝的象征。

祈年殿的主体建筑四周,墙外低楼,空间开阔,祈年殿和圈丘的整个外轮廓直接与天空连接,祭坛仿佛高入云霄,人站在祭坛上也好像升上青天。天坛的崇高感中,蕴含着敬天的思想。

“圈”不仅指外形,而且是一种科学境界。在中国古代美学中,阅代表着生命光转,蕴含着宇宙万物,体现了一种“天行健”的思想以及祥和的精神。

天坛建筑群的一个突出特征是大量圆的造型。圆丘 皇穹宇 祈年殿都是圆形,每一个建筑又形成很多同心圆 一直扩展到与穹隆形的天空成为一个圆融的整体。

“清”是天的一种特征,也是中国古代的一种美学范畴,体现一种人格精神或艺术境界,例如清新 清真 清淡 清妙等。“清”由“青”而来,通常我们称天是“青天” “蓝天” “苍天”。天坛的基本色调整体是青色,不论是天空还是琉璃瓦都属于青色。“青”是祥和 安宁的象征,也体现了一种空灵的美。

天坛建筑中,祈年殿 皇穹宇都采用蓝色琉璃瓦,深蓝的琉璃和浅蓝的天空形成色彩上深浅的对比 更显示出天的澄清 明朗。反过来天的澄清 明朗,又与祈年殿的外轮廓虚实相生,唤起观赏者的审美想象。

以上高 圆 清三点体现了天坛的崇高 祥和 清朗的独特意境。如果比较一下,就会发现:故宫拥有庞大的建筑群以,以气热取脏,天坛的建筑少而精,以宁静深远而著称;故宫以封闭式的一道道门 一道道墙为特点,而天坛以天高地阔的开放式为特点;故宫的空间徒刑是方的,而天坛则是柔和的圆;故宫的颜色以红为重,而天坛则是幽静的青绿色。天坛之美,耐人深思。

(取材于杨辛《天坛》)

小题1:.下列理解,符合文意的一项是

A.天坛的建筑风格是以气热高耸铺天盖地取胜。

B.故宫太和殿是明清两代北京的最高建筑,是帝王的象征。

C.天坛的大量圆形建筑表现了中国古人生生不息的宇宙观。

D.天坛的琉璃瓦采用蓝色,与蓝天相互融合,虚实相生。答:

小题2:.根据文意,下列对天坛建筑“高”这一特性的理解,正确的一项是

A.渐次升高,表示对上天的挑战。

B.节省占地面积,突出幽静之美。

C.高入云霄,表达“羽化登仙”的愿望。

D.突出崇高感,强化敬慕上苍的心情。答:

小题3:.作者从审美角度,指出天坛的意境是崇高 祥和 清朗,请你根据文章提示的故宫的建筑特点,也从审美角度,用三个双音词概括一下故宫的建筑意境。

答:                 ,                 ,                。

小题4:.天坛大约有十万株树,你认为这些树木的作用与本文所概括的“高 圆 清”三点中的哪一点关系最大?为什么?

答:                                                                         

阅读理解

I was sitting in the room reading when I heard a loud noise. To defend my home from break-in, I picked up my defense weapon--- a broom and went out. There on the roof of my porch(门廊), I saw a grey fluffy squirrel. I drove her away with the broom, but the next day I heard her again.

I searched squirrels on the net and found because their teeth keep growing, they have to constantly chew on things to shorten their teeth. This was disturbing so I asked my husband to call in some wildlife control people.

On Monday morning two men showed up, with guns in their hands. I pointed uneasily to the hole in my porch roof. They held up their guns. Suddenly I saw in my mind the baby nursery inside. I stopped them and confirmed that they wouldn’t harm her. They hesitated, but finally put down their guns. Then they brought out a bottle of deodorizer(除臭剂)and sprayed it into the squirrel’s home. They told me she would not like the smell and would leave.

There was no sign of Mrs. Squirrel, so they blocked the hole, took my cheque for $250 and left. Shortly after they left, Mrs. Squirrel returned from her shopping trip. She was mad at being driven out and began feverishly clawing at the porch roof. In order to stop the destruction of my home, I drove her away with the broom again.

Each day thereafter, Mrs. Squirrel continued her attack on my possession. I then called the company to report that “SHE’S BAAAAAACK…” The receptionist said that if Mrs. Squirrel had managed to find another way into my porch roof, it would be a new charge. I replied I couldn’t continue contributing my husband’s hard-earned income to their silly wildlife experts and hang up.

I went to the porch and banged on the roof. Mrs. Squirrel came out and glared at me. We negotiated some terms, came to an agreeable arrangement and went back into our respective homes.

All is quiet these days, although large quantities of materials have been removed from my garage wall and my daughter claims that some of her doll-house furniture has disappeared. I still hope that Mrs. Squirrel would leave, but I will wait until it is warmer and hopefully until after the birth of the little ones.

小题1:What did the author think of the squirrel at first?

A.Troublesome.

B.Dangerous.

C.Interesting.

D.Clever.小题2:Why didn’t the author ask the wildlife control people to come again?

A.She worried about the safety of the squirrel.

B.She thought the company charged too much.

C.She decided to drive away the squirrel herself.

D.She doubted the ability of the wildlife control people.小题3:What can we learn from the passage?

A.Getting rid of the squirrel needs patience.

B.The squirrel has destroyed the author’s house.

C.The author has developed affection for the squirrel.

D.The author singed an agreement with Mrs. Squirrel.小题4:The author has written the passage in a (an) ________ way.

A.persuasive

B.serious

C.informative

D.amusing