问题 单项选择题

下列有关酶的别构调节,错误的是()

A.受别构调节的酶称别构酶

B.别构酶多是关键酶(限速酶),催化的反应常是不可逆反应

C.别构酶催化的反应,其反应动力学是符合米-孟氏方程的

D.别构调节是快速调节

E.别构调节不引起酶的构型变化

答案

参考答案:C

解析:

参阅[2004N027]。但应注意: ①普通酶促反应动力学方程式为米氏方程:,反应速度与底物浓度的曲线为矩形双曲线;别构调节的反应方程式不符合米氏方程,其速度方程式为:(其中n为每个酶分子能结合作用物分子的数目,K为常数),反应速度与底物浓度的曲线呈S形。因此,C项错。 ②别构调节和酶的共价修饰都是酶的快速调节(D对)。 ③别构调节可引起酶的构象变化,而不引起酶的构型变化,因构象是指空间结构,构型是指一级结构。如 5版生物化学P95有关“磷酸化酶的别构调节就引起酶的构象变化”。

阅读理解

Honey from the African forest is not only a kind of natural sugar, it is also delicious.

Most people, and many animals, like eating it. However, the only way for them to get that honey is to find a wild bees' nest and take the honey from it. Often, these nests are high up in trees, and it is difficult to find them. In parts of Africa, though, people and animals looking for honey have a strange and unexpected helper - a little bird called a honey guide.

The honey guide does not actually like honey, but it does like the wax in the beehives (蜂房). The little bird cannot reach this wax, which is deep inside the bees' nest. So, when it finds a suitable nest, it looks for someone to help it. The honey guide gives a loud cry that attracts the attention of both passing animals and people. Once it has their attention, it flies through the forest, waiting from time to time for the curious animal or person as it leads them to the nest. When they finally arrive at the nest, the follower reaches in to get at the delicious honey as the bird patiently waits and watches. Some of the honey, and the wax, always fall to the ground, and this is when the honey guide takes its share.

Scientists do not know why the honey guide likes eating the wax, but it is very determined in its efforts to get it. The birds seem to be able to smell wax from a long distance away. They will quickly arrive whenever a beekeeper is taking honey from his beehives, and will even enter churches when beeswax candles are being lit.

小题1:Why is it difficult to find a wild bees' nest?

A.It's small in size.

B.It's hard to recognize.

C.It's covered with wax.

D.It's hidden in trees.小题2:What do the words "the follower" in Paragraph 2 refer to?

A.A bee.

B.A honey seeker.

C.A bird.

D.A beekeeper.小题3:The honey guide is special in the way ________.

A.it goes to church

B.it gets its food

C.it sings in the forest

D.it reaches into bees' nests小题4:What can be the best title for the text?

A.Wild Bees

B.Wax and Honey

C.Beekeeping in Africa

D.Honey-Lover's Helper

选择题