1. Which of the following titles best summarizes the contents of the passage?(A) Neurotransmitters: Their Crucial Function in Cellular Communication
This option talks about neurotransmitters in general but in the passage we are talking about a specific kind of neurotransmitter- Serotonin.
(B) Diet and Survival: An Old Relationship Reexamined.
Completely out of scope. No where in the passage survival is talked about(C) The Blood Supply and the Brain: A Reciprocal Dependence.
This passage is about the release of serotonin and tryptophan in brain with respect to various types of food. Hence this option is out of scope.(D) Amino Acids and Neurotransmitters: The Connection between Serotonin Levels and Tyrosine
The Connection between Serotonin Levels and Tyrosine is used as a case in point for the main point of the passage.
(E) The Effects of Food Intake on the Production and Release of Serotonin: Some Recent Findings
Exactly the gist of the passage.2. According to the passage, the speed with which tryptophan is provided to the brain cells of a rat varies with the(A) amount of protein present in a meal
Quote:
The more protein is in a meal, the lower is the ratio of the resulting blood-tryptophanconcentration to the concentration of competing amino acids, and the more slowly is tryptophan provided to the brain.
The above line talks about speed in the context of protein meal. Hence A is the answer.(B) concentration of serotonin in the brain before a meal
The author says that the concentration of serotonin increases after a carbohydrate meal but nothing about its concentration before a mean and its speed.(C) concentration of leucine in the blood rather than with the concentration of tyrosine in the blood after a meal
The author mentions leucine and tyrosine as examples of a mechansim he was explaining. Tyrosine and leucine concentration have nothing to do with the speed with which tryptophan is provided to the brain cells of a rat.Quote:
This same mechanism also provides the brain cells with other amino acids found in protein, such as tyrosine and leucine.
(D) concentration of tryptophan in the brain before a meal
Again concentration of tryptohan in the brain before a meal was never implied in the passage.(E) number of serotonin-containing neurons
This number is never mentioned in the passage let alone in the context of speed with which tryptophan is provided to the brain cells of a rat.3. According to the passage, when the authors began their first studies, they were aware thatOur first studies sought to determine whether the
increase in serotonin observed in rats
given a large injection of the amino acid tryptophan might also occur after rats ate meals that change tryptophan levels in the blood.
Since authors already know that with the injection of tryptophan, serotonin increases, they are hoping to finding out if the same happens in the case of food.
(A) they would eventually need to design experiments that involved feeding rats high concentrations of protein
Nothing about protein is mentioned in this part of the passage.(B) tryptophan levels in the blood were difficult to monitor with accuracy
Nothing about difficulty of monitoring.(C) serotonin levels increased after rats were fed meals rich in tryptophan.
Our first studies sought to determine whether the increase in serotonin observed in rats given a large injection of the amino acid tryptophan might also occur after rats ate meals that change tryptophan levels in the blood.
They don't already know it.They are hoping to finding out if serotonin levels increased after rats were fed meals rich in tryptophan. (D) there were many neurotransmitters whose production was dependent on metabolic processes elsewhere in the body.
Completely out of context.(E) serotonin levels increased after rats were injected with a large amount of tryptophan
Correct. According to the above quoted text from the passage, we can infer this.6. The authors' discussion of the "mechanism that provides blood tryptophan to the brain cells" (lines 34-35) is meant toQuote:
Since protein contains tryptophan, why should it depress brain tryptophan levels? The answer lies in the mechanism that provides blood tryptophan 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 author says since protein contains tryptophan and when one consumes protein, the tryptophan levels should increase in the brain. But that is not the case and he questions why. In the next line, he answers his question and says that 'due to the mechanism', this happens. So, he is mentioning 'mechanism' to explain why tryptophan levels are decreasing.
(A) stimulate further research studies
Nothing about further research was mentioned in the passage.(B) summarize an area of scientific investigation.
Authors are not summarizing.(C) help explain why a particular research finding was obtained
Yes. correct answer.(D) provide supporting evidence for a controversial scientific theory
Nothing controversial was mentioned in the passage.(E) refute the conclusions of a previously mentioned research study
The authors by saying that tryptophan levels decrease in the brain when protein rich meal is consumed, are not refuting the fact that tryptophan levels increase in the brain when meals elicit insulin secretion (mentioned in the previous passage). He is merely explaining the effect of protein on tryptophan production in brain.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
Quote:
Surprisingly, however, when we added a large amount of protein to the meal, brain tryptophan and serotonin levels fell.
Hence the right answer.(B) Meals consisting almost exclusively of carbohydrates
This is likely suitable. Hence , not the answer.(C) Meals that would elicit insulin secretion
This is most likely suitable. Hence , not the answer.(D) Meals that had very low concentrations of tyrosine
Out of scope. We do not know the effects of tyrosine in production and release of sorotonin.(E) Meals that had very low concentrations of leucine
Out of scope. We do not know the effects of leucine in production and release of sorotonin.
Updated on: 14 Mar 2021, 09:44
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