关于氨基酰-tRNA合成酶的特点正确的是（）。 A.催化的反应需要G_爱下问搜题

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问题单项选择题 A1/A2型题

关于氨基酰-tRNA合成酶的特点正确的是（）。

A.催化的反应需要GTP供能

B.可以水解酯键校正氨基酸和tRNA之间的错配

C.只对氨基酸有绝对专一性

D.只对tRNA有绝对专一性

E.总共有20种酶分别催化20种氨基酸和对应的tRNA的连接

答案

参考答案：B

解析：该酶在ATP的存在下，能催化氨基酸的活化以及与对应tRNA的结合反应。氨基酰tRNA合成酶位于胞液，具有绝对专一性，对氨基酸及tRNA都能高度特异地识别。因此，在胞液中至少有20种以上的氨基酰-tRNA合成酶，这些酶的高度专一性是保证翻译准确性的关键因素。

阅读理解

Cheating happens a lot in our city. It can be hard to know who is really in   1  and who is trying to take advantage of other people's    2  .
Recently, I was finishing my work at home    3  the dog barked letting me know that   4  was at the gate. I rushed to see who it was and there I saw a   5  weak woman in her late fifties. I said to her, "May I ask you what you   6 ?" She   7  , "Hello, my name is Mary. My husband and I live in the slum nearby. We earn our living   8  working at construction sites. A few days ago my   9  tripped on the stairs while
10 a heavy load. He is   11  hurt and hasn't been able to 12 for the past five days, so we have no food. Now he is at home in bed with a high fever. Please help me! I need to take my husband to a doctor!"
"Oh!" I said. "Please 13  here." I went into the room. I felt really bad about her 14 but--- Was she telling me the   15  or trying to cheat me out of my money?
Finally, I   16 to help her. But first I said a simple prayer, "Dear Lord, you know 17 I earn my pennies, so please make sure that my hard earned money helps those who 18 need it. Amen." I went out with a fifty note and
19 it to her. The moment she got the money she broke down in tears. She took my hand and said, "May god bless you, my dear! Thank you so much!"
I was so   20 , and turned back to my work smiling.

小题2:A. braveness B. kindness C. interest D envy

问答题简答题

在《扩大国家免疫规划实施方案》中规定的工作目标是什么？