搜题请搜索小程序“爱下问搜题”
问题 多项选择题

下列有关酶的叙述，不正确的是（）

A.一般来说，活细胞都能产生酶

B.酶的基本组成单位都是氨基酸

C.酶能降低化学反应的活化能

D.酶在细胞内才起催化作用

答案

参考答案：B, D

解析：

大多数的酶是蛋白质少数酶是RNA，所以其基本单位是氨基酸和核糖核苷酸，B错误。酶在细胞内外都有催化作用，D错误，AC正确。本题选BD。

考点：酶的概念和作用

单项选择题

In June 1985, two British mountaineers Joe Simpson and Simon Yates made the first-ever climb of the 21,000-foot snow-covered Siula Grande mountain in Peru. It was an exceptionally (26) job, but nothing compared to what was to (27) . Early in the process, Simpson (28) and broke his right knee. Yates could have (29) him but managed to find a way of (30) him down the mountains on a rope in a series of difficult drops. Then Simpson fell into a crevasse and Yates eventually had no (31) but to cut the (32) , completely convinced that his friend was now (33)

In his book on the (34) , Joe Simpson wrote:

(35) I looked at the distant moraines, I know that I must at least try I would probably (36) there among those rocks. If I died, well, that wasn’t so (37) , but I wouldn’t have (38) waited for it to happen. The (39) of dying no longer affected me as it had in the crevasse at first. I now had a chance to (40) it and struggle against it.

The survival of Yates himself was (41) . That Simpson somehow found a way of (42) out of the crevasse after 12 hours and then crawled and (43) himself six miles back to camp, (44) three days and might without food or drink, would be considered as a heroic fiction. But in fact it was so (45) .

36（）

A.stickout 

B.holdout 

C.hangout 

D.dieout
查看答案
单项选择题

下列可以减少替代品威胁的是( )。

A．成本领先战略
B．差别化战略
C．阵地式战略
D．重点集中化战略
查看答案