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GMAT_READING_COMPREHENSION

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GMAT READING COMPREHENSION SAMPLE QUESTIONS
Instruction: This file contains 285 sample questions on GMAT Reading Comprehension
and explanations for 24 of them. For answers with complete explanations to other 261
questions, please order the Complete GMAT Prep Course which includes Verbal Study
Guide, Essay Prep Course, and Math Review.
READING COMPREHENSION
Passage 1
Caffeine, the stimulant in coffee, has been called
"the most widely used psychoactive substance on Earth ."
Synder, Daly and Bruns have recently proposed that
caffeine affects behavior by countering the activity in
(5)

the human brain of a naturally occurring chemical called
adenosine. Adenosine normally depresses neuron firing
in many areas of the brain. It apparently does this by
inhibiting the release of neurotransmitters, chemicals
that carry nerve impulses from one neuron to the next.

(10)

Like many other agents that affect neuron firing,
adenosine must first bind to specific receptors on
neuronal membranes. There are at least two classes
of these receptors, which have been designated A1 and
A2. Snyder et al propose that caffeine, which is struc-

(15) turally similar to adenosine, is able to bind to both types
of receptors, which prevents adenosine from attaching
there and allows the neurons to fire more readily than
they otherwise would.
For many years, caffeine's effects have been attri(20) buted to its inhibition of the production of phosphodiesterase, an enzyme that breaks down the chemical
called cyclic AMP.A number of neurotransmitters exert
their effects by first increasing cyclic AMP concentrations in target neurons. Therefore, prolonged periods at
(25) the elevated concentrations, as might be brought about
by a phosphodiesterase inhibitor, could lead to a greater
amount of neuron firing and, consequently, to behavioral stimulation. But Snyder et al point out that the
caffeine concentrations needed to inhibit the production
(30) of phosphodiesterase in the brain are much higher than
those that produce stimulation. Moreover, other compounds that block phosphodiesterase's activity are not
stimulants.
To buttress their case that caffeine acts instead by pre(35) venting adenosine binding, Snyder et al compared the
stimulatory effects of a series of caffeine derivatives with
their ability to dislodge adenosine from its receptors in
1

the brains of mice. "In general," they reported, "the
ability of the compounds to compete at the receptors
(40) correlates with their ability to stim...
1
GMAT READING COMPREHENSION SAMPLE QUESTIONS
Instruction: This file contains 285 sample questions on GMAT Reading Comprehension
and explanations for 24 of them. For answers with complete explanations to other 261
questions, please order the Complete GMAT Prep Course
which includes Verbal Study
Guide, Essay Prep Course, and Math Review.
READING COMPREHENSION
Passage 1
Caffeine, the stimulant in coffee, has been called
"the most widely used psychoactive substance on Earth ."
Synder, Daly and Bruns have recently proposed that
caffeine affects behavior by countering the activity in
(5) the human brain of a naturally occurring chemical called
adenosine. Adenosine normally depresses neuron firing
in many areas of the brain. It apparently does this by
inhibiting the release of neurotransmitters, chemicals
that carry nerve impulses from one neuron to the next.
(10) Like many other agents that affect neuron firing,
adenosine must first bind to specific receptors on
neuronal membranes. There are at least two classes
of these receptors, which have been designated A1 and
A2. Snyder et al propose that caffeine, which is struc-
(15) turally similar to adenosine, is able to bind to both types
of receptors, which prevents adenosine from attaching
there and allows the neurons to fire more readily than
they otherwise would.
For many years, caffeine's effects have been attri-
(20) buted to its inhibition of the production of phosphodi-
esterase, an enzyme that breaks down the chemical
called cyclic AMP.A number of neurotransmitters exert
their effects by first increasing cyclic AMP concentra-
tions in target neurons. Therefore, prolonged periods at
(25) the elevated concentrations, as might be brought about
by a phosphodiesterase inhibitor, could lead to a greater
amount of neuron firing and, consequently, to behav-
ioral stimulation. But Snyder et al point out that the
caffeine concentrations needed to inhibit the production
(30) of phosphodiesterase in the brain are much higher than
those that produce stimulation. Moreover, other com-
pounds that block phosphodiesterase's activity are not
stimulants.
To buttress their case that caffeine acts instead by pre-
(35) venting adenosine binding, Snyder et al compared the
stimulatory effects of a series of caffeine derivatives with
their ability to dislodge adenosine from its receptors in
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