XDF补充材料25－8

csvqr

A选项exclusively of protein是指含有蛋白质还是不含蛋白质亚？

看了gmat阅读精解的解释，说a是只含蛋白质，根据文章最后一句话所以是最不可能的。可是我查这个词组的意思，怎么觉得a的意思是除了蛋白质之外亚

It was once believed that the brain was independent

  of metabolic processes occurring elsewhere in the body.

  In recent studies, however, we have discovered that the

  production and release in brain neurons of the neuro-

(5) transmitter serotonin (neurotransmitters are compounds

  that neurons use to transmit signals to other cells)

  depend directly on the food that the body processes.

    Our first studies sought to determine whether the

  increase in serotonin observed in rats given a large injec-

(10)tion of the amino acid tryptophan might also occur after

  rats ate meals that change tryptophan levels in the

  blood. We found that, immediately after the rats began

  to eat, parallel elevations occurred in blood tryptophan,

  brain tryptophan, and brain serotonin levels. These find-

(15) ings suggested that the production and release of sero-

  tonin in brain neurons were normally coupled with

  blood-tryptophan increases. In later studies we found

  that injecting insulin into a rat’s bloodstream also caused

  parallel elevations in blood and brain tryptophan levels

(20) and in serotonin levels. We then decided to see whether

  the secretion of the animal’s own insulin similarly affected

  serotonin production. We gave the rats a carbohydrate-

containing meal that we knew would elicit insulin secre-

   tion. As we had hypothesized, the blood tryptophan

(25) level and the concentrations of tryptophan

   serotonin in the brain increased after the meal.

   Surprisingly, however, when we added a large

amount of protein to the meal, brain tryptophan and

   serotonin levels fell. Since protein contains tryptophan,

(30)  why should it depress brain tryptophan levels? The

   answer lies in the mechanism that provides blood tryp-

   tophan to the brain cells. This same mechanism also

   provides the brain cells with other amino acids found in

   protein, such as tyrosine and leucine. The consumption

(35) of protein increases blood concentration of the other

   amino acids much more, proportionately, than it does

   that of tryptophan. The more protein in the meal, the

   lower is the ratio of the resulting blood-tryptophan

   concentration to the concentration of competing amino

(40) acids, and the more slowly is tryptophan provided to

   the brain. Thus the more protein in a meal, the less

   serotonin subsequently produced and released.

8. It can be inferred from the passage that which of the

  following would be LEAST likely to be a potential

  source of aid to a patient who was not adequately

   producing and releasing serotonin?

  (A) Meals consisting almost exclusively of protein

  (B) Meals consisting almost exclusively of

     carbohydrates

  (C) Meals that would elicit insulin secretion

  (D) Meals that had very low concentrations of tyrosine

  (E) Meals that had very low concentrations of leucine

而今迈步从头越

A选项exclusively of protein是指含有蛋白质还是不含蛋白质亚？

看了gmat阅读精解的解释，说a是只含蛋白质，根据文章最后一句话所以是最不可能的。可是我查这个词组的意思，怎么觉得a的意思是除了蛋白质之外亚

A选项说的是只含蛋白质，不是除蛋白质以外。exclusively means only. For example:

The distributor is exculsively settled in BeiJing Market. means we have only one distribuor in BJ.

This sample room is exclusively for women. only used by women