Is it a GMAT passage? Guess not!!
Which of the following titles best summarizes the contents of the passage?Ans: "E" - Entire passage tried to show how the metabolic activity after consuming certain food released Serotonin.
A Neurotransmitters: Their Crucial Function in Cellular Communication
B Diet and Survival: An Old Relationship Reexamined
C The Blood Supply and the Brain: A Reciprocal Dependence
D Amino Acids and Neurotransmitters: The Connection Between Serotonin Levels and Tyrosine
E The Effects of Food Intake on the Production and Release of Serotonin: Some Recent Findings
2. According to the passage, the speed with which tryptophan is provided to the brain cells of a rat varies with theAns: "A" - The more protein in the meal the more slowly is tryptophan provided to the brain.
A amount of protein present in a meal
B concentration of serotonin in the brain before a meal
C concentration of leucine in the blood rather than on the concentration of tyrosine in the blood after a meal
D concentration of tryptophan in the brain before a meal
E number of serotonin-containing neurons present in the brain before a meal
3. According to the passage, when the authors began their first studies, they were aware thatAns: "E" - 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.
A they would eventually need to design experiments that involved feeding rats high concentrations of protein
B tryptophan levels in the blood were difficult to monitor with accuracy
C 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.
E serotonin levels increased after rats were injected with a large amount of tryptophan
We previously injected tryptophan that caused serotonin increase.
We want to study whether the serotonin will increase if the tryptophan is naturally produced by the body after consuming food.
4. According to the passage, one reason that the authors gave rats carbohydrates was toAns: "C"
A depress the rats' tryptophan levels
B prevent the rats from contracting diseases
C cause the rats to produce insulin
D demonstrate that insulin is the most important substance secreted by the body
E compare the effect of carbohydrates with the effect of proteins
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 secretion.
5. According to the passage, the more protein a rat consumes, the lower will be theAns: "B"
A ratio of the rat's blood-tryptophan concentration to the amount of serotonin produced and released in the rat's brain
B ratio of the rat's blood-tryptophan concentration to the concentration in its blood of the other amino acids contained in the protein
C ratio of the rat's blood-tyrosine concentration to its blood-leucine concentration
D number of neurotransmitters of any kind that the rat will produce and release
E number of amino acids the rat's blood will contain
The more protein in the meal, the lower is the ratio of the resulting blood-tryptophan concentration to the concentration of competing amino acids.
6. The authors' discussion of the "mechanism that provides blood tryptophan to the brain cells" (lines 31-32) is meant toAns: "B"
A stimulate further research studies
B summarize an area of scientific investigation
C help explain why a particular research finding was obtained
D provide supporting evidence for a controversial scientific theory
E refute the conclusions of a previously mentioned research study
Investigation was that the brain is provided with multiple amino acids. How? The same way as it did before for trypotophan.
7. According to the passage, an injection of insulin was most similar in its effect on rats to an injection ofAns: "D"
In later studies we found that injecting insulin into a rat's bloodstream also caused parallel elevations in blood and brain tryptophan levels and in serotonin levels.
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