咖啡因第2题它怎么就weaken了啊?

birbird11

佩服佩服佩服

HQBDPP

太强大了。看了中文也不行。。不懂啊。。

隽宝宝

我想问问文章中间的的To buttress their case that caffeine acts instead by preventing adenosine binding，是不是文章开头的内容意思说反了？CSnyder, Daly and Bruns have recently proposed that caffeine affect behavior by countering the activity in the human brain of a naturally occurring chemical called adenosine. 。。。There are at least two classes of these receptors, which have been designated A1 and A2. Snyder et al propose that caffeine, which is structurally similar to adenosine, is able to bind to both types of receptors, which prevents adenosine from attaching there and allows the neurons to fire more readily than they otherwise would.
文章开头说这些人提出了种新观点caffeine通过和receptors结合阻碍adenosine和receptors结合，从而起到刺激作用，但是后面又说支持他们的case：咖啡因作用并非阻碍A的binding作用。这里是不是矛盾？

wandering_wind

这篇真的好难 ls说的这个act instead by 是对第二段的回应，第二段说 caffeine's effect have been attribute to its inhibition of the production of phosphodiesterase. 然后第三段说 并不是inhibiting the production of phosphodiesterase 而是preventing adenosine binding

wjtwenzi

anjjule 发表于 2011-7-20 22:37
看到XDF课堂笔记上说"太难了,不要求做", 直接厥倒! 本来就做题做得愁苦满怀,还整个不要求做,看来什么事都不 ...

这题目我总结的时候都花了比一般题目两倍的功夫，XDF直接来一句太难了什么意思！有考虑过GMAT的感受吗？

jianghxsir

其实，这题答案的weaken手法已经在原文中出现过，即‘Snyder et al point out that the caffeine concentrations needed to inhibit the production of phophodiesterase in the brain are much higher than those that produce stimulation’.和答案D的逻辑都是一个套路，即：还没达到你提出理论假设的条件时，就已经有刺激作用产生了，说明刺激的产生与该假设无关。

小桃仁cherry

感谢nn分享，多读几遍真的理解了！