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The chemical adenosine is released by brain cells when those [#permalink]
 28 Jul 2009, 03:54
Question Stats:
16% (02:52) correct
83% (01:48) wrong based on 1 sessions
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?
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.
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.
C. Besides binding to sites in the brain, adenosine is known to be involved in
biochemical reactions throughout the body.
D. Some areas of the brain that are relatively inactive nonetheless release
some adenosine.
E. Stress resulting from a dangerous situation can preserve wakefulness even
when brain levels of bound adenosine are high.
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Re: chemical adenosine [#permalink]
28 Jul 2009, 04:26
IMO B 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. -Though the number of bindings are very large, but still the option is saying that it is at its lowest concentration. That clearly means that at higher concentration the number of bindings will be even much larger. This option doesn't support "Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of 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. -Correct. The researchers are saying that increase in binding makes people sleepy. This option is giving an example when a decrease in binding keeps people awake. Hence supporting the researchers work.C. Besides binding to sites in the brain, adenosine is known to be involved in biochemical reactions throughout the body. -Irrelevant.D. Some areas of the brain that are relatively inactive nonetheless release some adenosine. -Irrelevant. Referring to very small amount of adenosine. "Some areas...release some..."E. Stress resulting from a dangerous situation can preserve wakefulness even when brain levels of bound adenosine are high. -Irrelevant. Its talking about a one off case.
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Re: chemical adenosine [#permalink]
28 Jul 2009, 11:51
Yep B
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Re: chemical adenosine [#permalink]
28 Jul 2009, 13:51
bigoyal wrote: IMO B
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. -Correct. The researchers are saying that increase in binding makes people sleepy. This option is giving an example when a decrease in binding keeps people awake. Hence supporting the researchers work.
B only says that caffeine 'interferes' with the binding. Can we assume that it decreases the binding for it's so-called effect? For me this option only says that caffeine has some kind of effect on brain cells. OA pls?
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Re: chemical adenosine [#permalink]
28 Jul 2009, 14:32
Economist wrote: bigoyal wrote: IMO B
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. -Correct. The researchers are saying that increase in binding makes people sleepy. This option is giving an example when a decrease in binding keeps people awake. Hence supporting the researchers work.
B only says that caffeine 'interferes' with the binding. Can we assume that it decreases the binding for it's so-called effect? For me this option only says that caffeine has some kind of effect on brain cells. OA pls? I think in this context: interfere is used as "Come between so as to be hindrance or obstacle"(Wordweb dictionary meaning)
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Re: chemical adenosine [#permalink]
28 Jul 2009, 21:39
Economist wrote: bigoyal wrote: IMO B
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. -Correct. The researchers are saying that increase in binding makes people sleepy. This option is giving an example when a decrease in binding keeps people awake. Hence supporting the researchers work.
B only says that caffeine 'interferes' with the binding. Can we assume that it decreases the binding for it's so-called effect? For me this option only says that caffeine has some kind of effect on brain cells. OA pls? I think so, as it is mentioned in the option that "Caffeine....is known to interfere with the binding of adenosine to sites on brain cells"So if its interfering with the binding process, it surely will at least slow down the process of binding process, hence not letting it to increase.
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Re: chemical adenosine [#permalink]
28 Jul 2009, 21:43
bigoyal wrote: Economist wrote: bigoyal wrote: IMO B
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. -Correct. The researchers are saying that increase in binding makes people sleepy. This option is giving an example when a decrease in binding keeps people awake. Hence supporting the researchers work.
B only says that caffeine 'interferes' with the binding. Can we assume that it decreases the binding for it's so-called effect? For me this option only says that caffeine has some kind of effect on brain cells. OA pls? I think so, as it is mentioned in the option that "Caffeine....is known to interfere with the binding of adenosine to sites on brain cells"OA is B
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Re: chemical adenosine [#permalink]
29 Jul 2009, 03:28
Thanks ankur55..good question:) and thanks all for the discussion.
Actually I did some over-engineering..
I was between C and E. ( which are almost similar )
Now that I know the OA...I can understand the subtle difference. C says that X affects the cells ( increase or decrease, but most probably decreases the binding to have its effect ) and thereby causes wakefulness. So we are sure that wakefulness or sleep is affected by the binding.
E says that Y 'preserves' wakefulness inspite of high concentration. It does not say anything about the effect of Y on the cells. So may be something else is causing sleep. This actually weakens the argument.
Nice pattern for cause-effect CRs.
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Re: chemical adenosine [#permalink]
29 Jul 2009, 07:37
Good question.
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Re: chemical adenosine [#permalink]
12 Jul 2010, 04:55
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Re: chemical adenosine
[#permalink]
12 Jul 2010, 04:55
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