问题 单项选择题

关于关键酶下述描述错误的是()

A.关键酶常是变构酶

B.在代谢途径中活性最高

C.常位于代谢途径第一步反应

D.常催化单向反应

E.常是受激素调节的酶

答案

参考答案:B

解析:关键酶或限速酶是决定连续酶促反应的总速度或方向的酶。关键酶通常催化单向反应,且多为催化代谢途径的第一步反应或反应速度最慢的酶。调节因素常常通过改变限速酶的活性来调节整个代谢通路。

阅读理解与欣赏

       孟尝君有舍人而弗悦,欲逐之。鲁连谓盂尝君日:“猿猴错木据水,则不若鱼鳖;历险乘危,则骐骥不如狐狸。曹沫奋三尺之剑,一军不能当。使曹沫释其三尺之剑,而操铫鎒与农夫居垅亩之中,则不若农夫。故物舍其所长之其所短尧亦有所不及矣。今使人而不能,则谓之不肖;教人而不能,则谓之拙。拙则罢之,不肖则弃之,使人有弃逐,不相与处,而来害相报者,岂用世立教之道哉?”孟尝君日:“善!”乃弗逐。

      【注释】:①错:同“措”,放弃。②铫鎒(yáo nòu):农具。

1、解释下列语句中划线词语的含义。

(1)使曹沫其三尺之剑                      

(2)乃逐                       

2、文中划线部分没有标点符号,请在需要加标点的地方用“/”标出来。

      故物舍其所长之其所短尧亦有所不及矣。

3、从论证方法的角度看,文中鲁连对孟尝君说:“猿猴错木据水,则不若鱼鳖;历险乘危,则骐骥不如狐狸。”用了什么说理方法来说服孟尝君的?有什么作用?

                                                                                                                                                             

                                                                                                                                                              

4、该故事给了你怎样的启示?

                                                                                                                                                               

单项选择题

Young girls at high risk for depression appear to have a malfunctioning reward system in their brains, a new study suggests. The finding comes from research that (1) a high-risk group of 13 girls, aged 10 to 14, who were not depressed but had mothers who (2) recurrent depression and a low-risk group of 13 girls with no (3) or family history of depression. Both groups were given MRI brain (4) while completing a task that could (5) either reward or punishment.

(6) with girls in the low-risk group, those in the high-risk group had (7) neural responses during both anticipation and receipt of the reward. (8) , the high-risk girls showed no (9) in an area of the brain called the dorsal anterior cingulated cortex (背侧前扣带皮质), believed to play a role in (10) past experiences to assist learning.

The high-risk girls did have greater activation of this brain area (11) receiving punishment, compared with the other girls. The researchers said that this suggests that high-risk girls have easier time (12) information about loss and punishment than information about reward and pleasure.

"Considered together with reduced activation in the striatal (纹状体的) areas commonly observed (13) reward, it seems that the reward-processing system is critically (14) in daughters who are at elevated risk for depression, (15) they have not yet experienced a depressive (16) ," wrote Ian H. Gotlib, of Stanford University, and his colleagues. " (17) , longitudinal studies are needed to determine whether the anomalous activations (18) in this study during the processing of (19) and losses are associated with the (20) onset of depression," they concluded. The study was published in the April of the Archives of General Psychiatry.

14()

A.repaired

B.impaired

C.healed

D.damaged