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neutronstar
Joined: 01 Mar 2015
Last visit: 27 Oct 2025
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08 Jun 2021, 20:40
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My Notes
1. Active Brain Cells --> Chemical Adenosine (CA) --> wakefulness = amount released (more) => binds (more) sites on cell
2. Sleep = binding (decreased)
3. Hypothesis = binding over large sites results in the beginning (onset) of sleep
Question
The chemical adenosine is released by brain cells when those cells are active. Adenosine then binds to more and more sites on cells in certain areas of the brain, as the total amount released gradually increases during wakefulness. During sleep, the number of sites to which adenosine is bound decreases. Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep.
Which of the following, if true, provides the most support for the researchers’ hypothesis?
Pre thinking - I need something that suggests binding over large sites results in the 'beginning' of sleep or something that controls in binding over large sites and 'defers' the sleep
(A) Even after long periods of sleep when adenosine is at its lowest concentration in the brain, the number of brain cells bound with adenosine remains very large.
it speaks about 'after long periods of sleep' - may not be helpful to prove what begins sleep
(B) Caffeine, which has the effect of making people remain wakeful, is known to interfere with the binding of adenosine to sites on brain cells.
If caffeine interferes with binding, large binding may not happen and sleep may be deferred - I will keep this option and evaluate other options.
(C) Besides binding to sites in the brain, adenosine is known to be involved in biochemical reactions throughout the body.
I should not care in what other things CA is involved unless it is connected to sleep.
(D) Some areas of the brain that are relatively inactive nonetheless release some adenosine.
I need something to connect the site/area and sleep. In a given choice, I do not get that causal relation.
(E) Stress resulting from a dangerous situation can preserve wakefulness even when brain levels of bound adenosine are high.
It says not always large binding will result in the onset of sleep. Exception is 'stress situations'. Not very helpful.
1. Active Brain Cells --> Chemical Adenosine (CA) --> wakefulness = amount released (more) => binds (more) sites on cell
2. Sleep = binding (decreased)
3. Hypothesis = binding over large sites results in the beginning (onset) of sleep
Question
The chemical adenosine is released by brain cells when those cells are active. Adenosine then binds to more and more sites on cells in certain areas of the brain, as the total amount released gradually increases during wakefulness. During sleep, the number of sites to which adenosine is bound decreases. Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep.
Which of the following, if true, provides the most support for the researchers’ hypothesis?
Pre thinking - I need something that suggests binding over large sites results in the 'beginning' of sleep or something that controls in binding over large sites and 'defers' the sleep
(A) Even after long periods of sleep when adenosine is at its lowest concentration in the brain, the number of brain cells bound with adenosine remains very large.
it speaks about 'after long periods of sleep' - may not be helpful to prove what begins sleep
(B) Caffeine, which has the effect of making people remain wakeful, is known to interfere with the binding of adenosine to sites on brain cells.
If caffeine interferes with binding, large binding may not happen and sleep may be deferred - I will keep this option and evaluate other options.
(C) Besides binding to sites in the brain, adenosine is known to be involved in biochemical reactions throughout the body.
I should not care in what other things CA is involved unless it is connected to sleep.
(D) Some areas of the brain that are relatively inactive nonetheless release some adenosine.
I need something to connect the site/area and sleep. In a given choice, I do not get that causal relation.
(E) Stress resulting from a dangerous situation can preserve wakefulness even when brain levels of bound adenosine are high.
It says not always large binding will result in the onset of sleep. Exception is 'stress situations'. Not very helpful.
01 Nov 2021, 07:02
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Ilishar
Even though I understand why B is correct, I had the exact same doubt about E. Could you pls explain why E is wrong?
GMATNinja VeritasKarishma
Thank you in Advance!
03 Nov 2021, 13:55
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Chitra657
The correct answer should support the hypothesis that "the cumulative binding of adenosine to a large number of sites... causes the onset of sleep."
Let's see how answer choice (E) affects this hypothesis.
Quote:
This tells us that stress from a dangerous situation can preserve wakefulness. But what does it tell us explicitly about adenosine? Not very much. It confirms that adenosine can bind to something in the brain, but we have no idea what effect this bound adenosine is having.
You mention that (E) implies that "high levels of adenosine cause the onset of sleep and stress counters it." But as you say, that is only an implication. Going by the exact words of (E), we really don't know what effect the binding of adenosine has. Maybe it reduces stress, but has nothing to do with sleep or wakefulness? Or maybe it doesn't even affect stress?
Going by the precise words in (E), we just can't say what effect adenosine has. So (E) is incorrect.
I hope that helps!
