本贴相关题目 TN-16-CR-36 (PGPE)

00:00:00

The chemical adenosine is released by brain cells when those cells are active. Adenosine then binds to more and more sites on cells in certain areas of the brain, as the total amount released gradually increases during wakefulness. During sleep, the number of sites to which adenosine is bound decreases. Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep.

Which of the following, if true, provides the most support for the researchers' hypothesis?

AEven after long periods of sleep when adenosine is at its lowest concentration in the brain, the number of brain cells bound with adenosine remains very large.
BCaffeine, which has the effect of making people remain wakeful, is known to interfere with the binding of adenosine to sites on brain cells.
CBesides binding to sites in the brain, adenosine is known to be involved in biochemical reactions throughout the body.
DSome areas of the brain that are relatively inactive nonetheless release some adenosine.
EStress resulting from a dangerous situation can preserve wakefulness even when brain levels of bound adenosine are high.

正确答案: B

请教gwd一题

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peter3008

楼主

发表于 2010-8-5 06:28:40 | 显示全部楼层

自己刚刚也做了这题，我猜得是B，不过读题的时候，我觉得前提跟结论有矛盾，所以怎么也逻辑不起来，先来分析一下我之前错误的理解：
前提：A bind to more and more site (bind increase)----> wakefulness (not sleep)
sleep---> bind decrease

结论：bind A ---> 导致睡眠 (而根据前提，bind A--->not sleep) 有矛盾阿

关键是这个cumulative词，这个就是lawyer所说的结论具体性，cumulative说明的是积累的binding A 导致睡眠，怎么去理解呢？it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep。结论句。睡觉的成因是Adenosine与许多sites的cumulative binding。
而前提说明的binding的增加或减少正是 cumulative binding的一种动态的体现，容易误解的是bind在一起就是not sleep，不bind的在一起就是sleep,即使bind在一起，也需要积累到一定量才能导致睡觉，再积累到一定的量就是not sleep,这个是个渐变的过程，不是跟开关一样，一开一关。