问题 单项选择题

干扰IMP-AMP的核苷酸抗代谢物是

A.6-巯基嘌呤
B.氮杂丝氨酸
C.别嘌呤醇
D.甲氨蝶呤

答案

参考答案:A

解析: 本题考察嘌呤和嘧啶核苷酸的抗代谢物的作用。干扰duMP—dTMP的核苷酸抗代谢物是甲氨蝶呤(MTX)和5-氟尿嘧啶(5-Fu)。干扰IMP一AMP的核苷酸抗代谢物是6-巯基嘌呤(6MP)。氮杂丝氨酸干扰IMP的合成、IMP—GMP及UTP—CTP的反应。而别嘌呤醇是黄嘌呤氧化酶的抑制剂,其影响尿酸的生成。

阅读理解

阅读理解。

Skin-diving (潜水) is a new sport today. This sport takes you into a wonderful new world. It is like a visit

to the moon. When you are under water, it is easy for you to climb big rocks (岩石), because you are no

longer (不再) heavy.

      Here, under water, everything is blue and green. In the day, there is much light. When fish swims

nearby (附近), you can catch them with your hands.

    When you have tanks (罐) of air on your back, you can stay in deep (深的) water for a long time. But

you must be careful when you dive in deep water.

     To catch fish is one of the most (最) interesting parts of this sport. Besides (除……之外), there are

more uses for skin-diving. You can clean ship without taking them out of water. You can get many things

from the deep sea. Now you see that skin-diving is both useful and interesting.

1. Skin-diving is a new sport. It can take you to _____. [ ]

A. the moon

B. a new world of land

C. the mountains (山脉)

D. deep water

2. In deep water _____. [ ]

A. there is much light

B. there is no light at all

C. you can find a lot of blue fish

D. everything looks blue and green

3. With tanks of air on your back, you can _____. [ ]

A. catch fish very easily

B. stay under water for a long time

C. climb big rocks

D. have more fun

4. From this passage, we can know _____.[ ]

A. we become fat

B. we become thin

C. we become lighter (更轻)

D. we become heavier (更重)

5. Which of the following is NOT true? [ ]

A. Skin-diving is a new sport.

B. Skin-diving is like a new sport.

C. The only use of skin-diving is to have more fun.

D. Skin-diving is interesting and useful.

单项选择题