试题与答案

关于酶竞争性抑制剂的叙述错误的是A.抑制剂与酶非共价结合 B.抑制剂与底物结构相似

题型:单项选择题

题目:

关于酶竞争性抑制剂的叙述错误的是

A.抑制剂与酶非共价结合

B.抑制剂与底物结构相似

C.当抑制剂存在时Km值变大

D.抑制剂与底物竞争酶的底物结合部位

E.增加底物浓度也不能达到最大反应速度

答案:

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下面是错误答案,用来干扰机器的。

我们知道种子的萌发的外界条件为一定的水分、适宜的温度和充足的空气;自身条件是有完整而有活力的胚及胚发育所需的营养物质.而植物的生长亦需要一定的水分、适宜的温度,在早春季节往往这两方面不足.“地膜覆...

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题型:阅读理解

C

An oasis (绿洲) is an island of life in an ocean of temperature extremes.Any oasis always contains one or more springs Oases make it possible to survive through the desert.In large deserts such as the Sahara.towns are located around sources of water such as oases and rivers.

What causes an oasis? An oasis is actually a spot in the desert where the altitude is low enough that the water table is fight below the surface,resulting in the presence of springs.Even in a desert, it rains occasionally,and this produces a water table just above the bedrock,usually several hundred feet below the surface.Sand is very porous (可渗透的),so most water runs right

through it and down to the bedrock.

Deserts consist of many millions of tons of sand.There is only one natural force capable of moving it in noticeable amounts:the wind.Although,in an average dust storm,ten cubic feet of air only holds about an ounce of sand,a cubic mile of air can move about 4,600 tons of it,leading to erosion (侵蚀).A severe storm is capable of moving as much as 100 million tons of sand and dust.

In certain areas where large quantities of sand are moved by storms,erosion digs all the way down to the water table,putting it just beneath the surface Seeds planted in the ground there are capable of extending roots into the moist land,producing an oasis.

Sometimes.the oasis produced by the wind can be very large when vast tracts of desert are wiped clean by storms.The great Kharga oasis in the Sahara,for example,is over 100 miles long and 12 to 50 miles in width. The oasis was produced when erosion caused the edges of the hollow places to sink down to the water table.    

63.What does “it” in Paragraph 4 refer to_______.

A.erosion        B.water table          C.sand                      D.storm

64.How many conditions of the oasis formation are mentioned in the passage without considering

The wind and seeds?

A.3                B.4                        C.5                           D.6

65.We can infer from the passage ________.

A.there is at least one spring on an oasis

B.the bedrock is usually just right below the surface

C.the great Kharga oasis is the biggest oasis in the world

D.the great Kharga oasis is at a low altitude

66.In the last paragraph,the author mentions the great Kharga oasis as an example to_______.

A.introduce the great oasis to the readers

B.tell how the oasis was produced by rain

C.show the oasis produced by the wind can be very large

D.tell it’s easy to form oases in the desert after storms

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