Passage Reading and English Comprehension
(a) Neurotransmitters: Their Crucial Function in Cellular Communication
(b) Diet and Survival: An Old Relationship Reexamined
(c) The Effects of Food Intake on the Production and Release of Serotonin: Some Recent Findings
(d) The Blood Supply and the Brain: A Reciprocal Dependence
163. 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
(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
164. According to the passage, when the authors began their first studies, they were aware that
(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) serotonin levels increased after rats were injected with a large amount of tryptophan
165. According to the passage, one reason that the authors gave rats carbohydrates was to
(a) depress the ratsí 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
166. According to the passage, the more protein a rat consumes, the lower will be the
(a) ratio of the ratís blood-tryptophan concentration to the amount of serotonin produced and released in the ratís brain
(b) ratio of the ratís blood-tryptophan concentration to the concentration in its blood of the other amino acids contained in the protein
(c) ratio of the ratís blood-tyrosine concentration to its blood-leucine concentration
(d) number of neurotransmitters of any kind that the rat will produce and release
167. The authorsí discussion of the ďmechanism that provides blood tryptophan to the brain cellsĒ 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
168. According to the passage, an injection of insulin was most similar in its effect on rats to an injection of
169. 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
170. 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?
(a) The ratsí brain serotonin levels would not decrease.
(b) The ratsí brain tryptophan levels would decrease.
(c) The ratsí tyrosine levels would increase less quickly than would their leucine levels.
(d) The rats would produce more insulin.
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