Directions (1-9): Read the following passage carefully and choose
the best answer to each question out of the five given alternatives.
the best answer to each question out of the five given alternatives.
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
neurotransmitter serotonin (neurotransmitters are compounds that neurons use to
transmit signals to other cells) depend directly on the food that the body
processes.
processes occurring elsewhere in the body. In recent studies, however, we have
discovered that the production and release in brain neurons of the
neurotransmitter 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 injection 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 findings suggested that the production and release of serotonin
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 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 secretion. As we
had hypothesized, the blood tryptophan level and the concentrations of
tryptophan and of serotonin in the brain increased after the meal.
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. We found that immediately after the rats began to eat, parallel
elevations occurred in blood tryptophan, brain tryptophan, and brain serotonin
levels. These findings suggested that the production and release of serotonin
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 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 secretion. As we
had hypothesized, the blood tryptophan level and the concentrations of
tryptophan and of 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, 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 consumption of protein increases the
blood concentration of the other amino acids much more, proportionately, than
it does that of tryptophan. The more protein is in a meal, the lower is the
ratio of the resulting blood-tryptophan concentration to the concentration of
competing for amino 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.
the meal, brain tryptophan, and serotonin levels fell. 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 consumption of protein increases the
blood concentration of the other amino acids much more, proportionately, than
it does that of tryptophan. The more protein is in a meal, the lower is the
ratio of the resulting blood-tryptophan concentration to the concentration of
competing for amino 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.
Q1. Which of the following titles best summarizes the contents of
the passage?
the passage?
(a) Neurotransmitters: Their Crucial Function in Cellular
Communication
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
Serotonin Levels and Tyrosine
(e) The Effects of Food Intake on the Production and Release of
Serotonin: Some Recent Findings
Serotonin: Some Recent Findings
Q2. According to the passage, the speed with which tryptophan is
provided to the brain cells of a rat varies with the
provided to the brain cells of a rat varies with the
(a) the amount of protein presents in a meal
(b) the concentration of serotonin in the brain before a meal
(c) the concentration of leucine in the blood rather than with the
concentration of tyrosine in the blood after a meal
concentration of tyrosine in the blood after a meal
(d) the concentration of tryptophan in the brain before a meal
(e) number of serotonin-containing neurons
Q3. According to the passage, when the authors began their first
studies, they were aware that
studies, they were aware that
(a) they would eventually need to design experiments that involved
feeding rats high concentrations of protein
feeding rats high concentrations of protein
(b) tryptophan levels in the blood were difficult to monitor with
accuracy
accuracy
(c) serotonin levels increased after rats were fed meals rich in
tryptophan
tryptophan
(d) there were many neurotransmitters whose production was
dependent on metabolic processes elsewhere in the body
dependent on metabolic processes elsewhere in the body
(e) serotonin levels increased after rats were injected with a
large amount of tryptophan
large amount of tryptophan
Q4. According to the passage, one reason that the authors gave
rats carbohydrates was to
rats carbohydrates was to
(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
secreted by the body
(e) compare the effect of carbohydrates with the effect of
proteins
proteins
Q5. According to the passage, the more protein a rat consumes, the
lower will be the
lower will be the
(a) the ratio of the rat’s blood-tryptophan concentration to the
amount of serotonin produced and released in the rat’s brain
amount of serotonin produced and released in the rat’s brain
(b) the ratio of the rat’s blood-tryptophan concentration to the
concentration in its blood of the other amino acids contained in the protein
concentration in its blood of the other amino acids contained in the protein
(c) the ratio of the rat’s blood-tyrosine concentration to its
blood-leucine concentration
blood-leucine concentration
(d) number of neurotransmitters of any kind that the rat will
produce and release
produce and release
(e) number of amino acids the rat’s blood will contain
Q6. The authors’ discussion of the “mechanism that provides blood
tryptophan to the brain cells” is meant to
tryptophan to the brain cells” is meant to
(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
theory
(e) refute the conclusions of a previously mentioned research
study
study
Q7. According to the passage, an injection of insulin was most
similar in its effect on rats to an injection of
similar in its effect on rats to an injection of
(a) tyrosine
(b) leucine
(c) blood
(d) tryptophan
(e) protein
Q8. 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?
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
Q9. It can be inferred from the passage that the authors
initially held which of the following hypotheses about what would happen when
they fed large amounts of protein to rats?
initially held which of the following hypotheses about what would happen when
they fed large amounts of protein to rats?
(a) The rats’ brain serotonin levels would not decrease.
(b) The rats’ brain tryptophan levels would decrease.
(c) The rats’ tyrosine levels would increase less quickly than
would their leucine levels.
would their leucine levels.
(d) The rats would produce more insulin.
(e) The rats would produce neurotransmitters other than serotonin.
Directions (10-15): Choose the option which is the antonym of the
word mentioned in the question.
word mentioned in the question.
Q10. Fledgling
(a) lobbyist
(b) sophomoric
(c) veteran
(d) sapling
(e) green horn
Q11. Apathy
(a) nonchalance
(b) rebuttal
(c) antipathy
(d) empathy
(e) fortune
Q12. Bucolic
(a) penalize
(b) censure
(c) punish
(d)
civic
civic
(e) rustic
Q13. Veneration
(a) dissuasion
(b) ignorance
(c) passivity
(d) contempt
(e) honour
Q14. Vitriolic
(a) humble
(b) retiring
(c) pleasant
(d) pure
(e) bitter
Q15. Soporific
(a) mature
(b) impervious
(c) exciting
(d) steep
(e) dull
