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655-705 Level|   Long Passage|   Science|                        
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Caffeine, the stimulant in coffee, has been called “the most widely us 03 Oct 2020, 13:17
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GMATNinja VeritasKarishma ChiranjeevSingh
Snyder et al. propose that caffeine, which is structurally 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

can you please explain here which refers to either receptor or caffeine.

according to meaning it should refer to caffeine but according to grammer rule it refers to receptors.
if it refers to caffeine how it can refer to very far away noun please give your insights
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Caffeine, the stimulant in coffee, has been called “the most widely us 16 May 2021, 01:12
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Quote:
Part of New RC Series- Please check this link for more questions

Caffeine, the stimulant in coffee, has been called “the most widely used psychoactive substance on Earth.” Snyder, Daly, and Bruns have recently proposed that caffeine affects behavior by countering the activity in 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.

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 structurally 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 attributed 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 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 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 preventing 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 the brains of mice. “In general,” they reported, “the ability of the compounds to compete at the receptors correlates with their ability to stimulate locomotion in the mouse; i.e., the higher their capacity to bind at the receptors, the higher their ability to stimulate locomotion.” Theophylline, a close structural relative of caffeine and the major stimulant in tea, was one of the most effective compounds in both regards.

There were some apparent exceptions to the general correlation observed between adenosine receptor binding and stimulation. One of these was a compound called 3-isobutyl-1-methylxanthine (IBMX), which bound very well but actually depressed mouse locomotion. Snyder et al. suggest that this is not a major stumbling block to their hypothesis. The problem is that the compound has mixed effects in the brain, a not unusual occurrence with psychoactive drugs. Even caffeine, which is generally known only for its stimulatory effects, displays this property, depressing mouse locomotion at very low concentrations and stimulating it at higher ones.

Show SpoilerOA
D
Show SpoilerOE
71. A. The passage discusses a current investigation, not one planned for the future.
B. The passage examines two explanations, but the earlier theory is discussed only to expose its weakness and the diff erences between the explanations are not reconciled. Most of the passage is devoted to the more recent hypothesis.
C. Only two theories are presented in the passage.
D. Correct. Th e recent hypothesis provides an alternative to an earlier one and is supported by evidence and arguments.
E. Lines 32–37 do pose such a challenge to the earlier theory; however, the challenge is a small part of the whole passage. Similarly, in the final paragraph, an exception to the more recent theory is introduced, only to be dismissed as an unimportant concern.

The correct answer is D.

1. The primary purpose of the passage is to

(A) discuss a plan for investigation of a phenomenon that is not yet fully understood
(B) present two explanations of a phenomenon and reconcile the differences between them
(C) summarize two theories and suggest a third theory that overcomes the problems encountered in the first two
(D) describe an alternative hypothesis and provide evidence and arguments that support it
(E) challenge the validity of a theory by exposing the inconsistencies and contradictions in it


Show SpoilerOA
D
Show SpoilerOE
72. A. The passage does not suggest that adenosine stimulates behavior.
B. While the final paragraph reveals that caffeine displays mixed eff ects, the passage does not state that adenosine has a stimulatory effect.
C. Increasing cyclic AMP concentrations is part of the earlier theory, not that of Snyder et al.
D. Correct. Lines 17–21 explain that caffeine binds to the receptors, releasing neurotransmitters, whereas adenosine hinders that release.
E. Inhibiting the production of phosphodiesterase is discussed in the earlier theory, not in the work of Snyder et al.

The correct answer is D.
2. According to Snyder et al., caffeine differs from adenosine in that caffeine

(A) stimulates behavior in the mouse and in humans, whereas adenosine stimulates behavior in humans only
(B) has mixed effects in the brain, whereas adenosine has only a stimulatory effect
(C) increases cyclic AMP concentrations in target neurons, whereas adenosine decreases such concentrations
(D) permits release of neurotransmitters when it is bound to adenosine receptors, whereas adenosine inhibits such release
(E) inhibits both neuron firing and the production of phosphodiesterase when there is a sufficient concentration in the brain, whereas adenosine inhibits only neuron firing


Show SpoilerOA
A
Show SpoilerOE
73. A. Correct. The results of one experiment can be explained by mixed eff ects in the brain, which Snyder et al. say may occur with psychoactive drugs.
B. This response refers back to the earlier theory, not to Snyder et al.’s response concerning IBMX experiment results.
C. Caffeine is only included within the broad category of psychoactive drugs.
D. This effect is attributed to one compound,IBMX, not to all psychoactive drugs.
E. This ability is not discussed in the passage.

The correct answer is A.
3. In response to experimental results concerning IBMX, Snyder et al. contended that it is not uncommon for psychoactive drugs to have

(A) mixed effects in the brain
(B) inhibitory effects on enzymes in the brain
(C) close structural relationships with caffeine
(D) depressive effects on mouse locomotion
(E) the ability to dislodge caffeine from receptors in the brain


Show SpoilerOA
E
Show SpoilerOE
74. A. Lines 54–55 state that IBMX binds to receptors.
B. Lines 17–19 state that caff eine binds to receptors.
C. Lines 13–14 state that adenosine binds to receptors.
D. Lines 46–50 state that theophylline binds to receptors.
E. Correct. The passage includes no evidence that phosphodiesterase binds to receptors.

The correct answer is E.
4. According to Snyder et al., all of the following compounds can bind to specific receptors in the brain EXCEPT

(A) IBMX
(B) caffeine
(C) adenosine
(D) theophylline
(E) phosphodiesterase


Show SpoilerOA
B
Show SpoilerOE
75. A. Phosphodiesterase is discussed in an entirely diff erent context in lines 22–25.
B. Correct. Lines 17–19 suggest that caffeine’s structural similarity to adenosine may be responsible for its ability to bind to A1 and A2 receptors.
C. Caff eine acts on neurotransmitters; it is not structurally similar to them.
D. Caffeine’s ability to stimulate behavior results from, rather than causes, this process.
E. The passage does not discuss the natural occurrence of these compounds.

The correct answer is B.
5. Snyder et al. suggest that caffeine’s ability to bind to A1 and A2 receptors can be at least partially attributed to which of the following?

(A) The chemical relationship between caffeine and phosphodiesterase
(B) The structural relationship between caffeine and adenosine
(C) The structural similarity between caffeine and neurotransmitters
(D) The ability of caffeine to stimulate behavior
(E) The natural occurrence of caffeine and adenosine in the brain


Show SpoilerOA
B
Show SpoilerOE
76. A. The quotation explains results of an experiment, not assumptions about a theory.
B. Correct. The quotation summarizes the experiment with mice and reports a major finding in support of the hypothesis.
C. The quotation generalizes on the basis of the experiment; it does not limit the finding to mice.
D. Specific, not general, correlations were made between the ability to bind to receptors and to stimulate locomotion.
E. The passage includes no such objections; therefore no refutations are needed.

The correct answer is B.
6. The author quotes Snyder et al.[highlighted] in lines 43–48 most probably in order to

(A) reveal some of the assumptions underlying their theory
(B) summarize a major finding of their experiments
(C) point out that their experiments were limited to the mouse
(D) indicate that their experiments resulted only in general correlations
(E) refute the objections made by supporters of the older theory

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Does this question only have 6 questions? I remember seeing this in an OG and recall 8 or 9 questions.. can someone confirm please?
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Caffeine, the stimulant in coffee, has been called “the most widely us 16 May 2021, 03:47
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Please someone explain in Detail Q2?
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Caffeine, the stimulant in coffee, has been called “the most widely us 16 May 2021, 19:39
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Please someone explain in Detail Q2?
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Hey junii, Perhaps citing the exact place where the answer (Option D) lies might help.

1. Caffeine (last sentence of the 2nd paragraph- "Snyder et al. propose that caffeine, which is structurally 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."

2. Adenosine (2nd to last sentence in the 1st paragraph) - "Adenosine normally depresses neuron firing in many areas of the brain."

I'm happy to help further if needed. :)
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Caffeine, the stimulant in coffee, has been called “the most widely us 23 Jul 2021, 23:35
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Can someone explain Q1 and Q6?
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Caffeine, the stimulant in coffee, has been called “the most widely us 24 Jul 2021, 01:08
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Official Explanation

1. The primary purpose of the passage is to

Difficulty Level: 700

Explanation

A. The passage discusses a current investigation, not one planned for the future.

B. The passage examines two explanations, but the earlier theory is discussed only to expose its weakness and the differences between the explanations are not reconciled. Most of the passage is devoted to the more recent hypothesis.

C. Only two theories are presented in the passage.

D. Correct. The recent hypothesis provides an alternative to an earlier one and is supported by evidence and arguments.

E. Lines 32–37 do pose such a challenge to the earlier theory; however, the challenge is a small part of the whole passage. Similarly, in the final paragraph, an exception to the more recent theory is introduced, only to be dismissed as an unimportant concern.

The correct answer is D.

6. The author quotes Snyder et al.[highlighted] in lines 43–48 most probably in order to

Difficulty Level: 700

Explanation

A. The quotation explains the results of an experiment, not assumptions about a theory.

B. Correct. The quotation summarizes the experiment with mice and reports a major finding in support of the hypothesis.

C. The quotation generalizes on the basis of the experiment; it does not limit the finding to mice.

D. Specific, not general, correlations were made between the ability to bind to receptors and to stimulate locomotion.

E. The passage includes no such objections; therefore no refutations are needed.

The correct answer is B.

AasthaSinghvi
Can someone explain Q1 and Q6?
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Caffeine, the stimulant in coffee, has been called “the most widely us 12 Feb 2022, 23:35
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Is this an official guide passage??

Posted from my mobile device
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Caffeine, the stimulant in coffee, has been called “the most widely us 13 Feb 2022, 07:40
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JenniferMassey
Is this an official guide passage??
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Hi JenniferMassey

Yes! this passage is from the official guide Verbal review 2016.

PS: You can see the source tag area to know the source of the question.
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Caffeine, the stimulant in coffee, has been called “the most widely us 09 Mar 2022, 21:28
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Is this actually a 600-700 level passage? I'm generally pretty good at RC but found this to be fairly challenging and I would have thought it was a 700-level passage if I didn't see the tags. Any thoughts on this?
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Caffeine, the stimulant in coffee, has been called “the most widely us 10 Mar 2022, 11:24
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UserMaple5
Is this actually a 600-700 level passage? I'm generally pretty good at RC but found this to be fairly challenging and I would have thought it was a 700-level passage if I didn't see the tags. Any thoughts on this?
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The following should be the difficulty level of each question, in my opinion.

Question #1: 700
Question #2: 700
Question #3: 500
Question #4: 600
Question #5: 600
Question #6: 700
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Caffeine, the stimulant in coffee, has been called “the most widely us 11 Mar 2022, 09:36
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This RC took me around 31 minutes to solve! Should I really appear on the test? However, I am not timing myself right now and I am in my early days of my preparation. On the bright side, I corrected 5 out of 6. :) :'(
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Caffeine, the stimulant in coffee, has been called “the most widely us 11 Mar 2022, 09:40
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Hi Sajjad1994, can you help me with the question no 6? I picked D because I assumed that the highlighted passage talked about correlations and I rejected B here since it did not talk about any experiments specifically.

6. The author quotes Snyder et al.[highlighted] in lines 43–48 most probably in order to

(A) reveal some of the assumptions underlying their theory
(B) summarize a major finding of their experiments
(C) point out that their experiments were limited to the mouse
(D) indicate that their experiments resulted only in general correlations
(E) refute the objections made by supporters of the older theory
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Caffeine, the stimulant in coffee, has been called “the most widely us 11 Mar 2022, 11:38
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Please read the explanation in the post in the link below

https://gmatclub.com/forum/caffeine-the ... l#p2827944

Thank you!

jarbit
Hi Sajjad1994, can you help me with the question no 6? I picked D because I assumed that the highlighted passage talked about correlations and I rejected B here since it did not talk about any experiments specifically.

6. The author quotes Snyder et al.[highlighted] in lines 43–48 most probably in order to

(A) reveal some of the assumptions underlying their theory
(B) summarize a major finding of their experiments
(C) point out that their experiments were limited to the mouse
(D) indicate that their experiments resulted only in general correlations
(E) refute the objections made by supporters of the older theory
Show more
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Caffeine, the stimulant in coffee, has been called “the most widely us 22 Aug 2022, 22:56
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Hi Experts,

GMATNinjaTwo
GMATNinja
KarishmaB

I have read the above explanations for Q6 and I'm still not able to figure out why the option is B and not A.

I thought the assumption is "the ability of the compounds to compete at the receptors correlates with locomotion." Thus, this is how caffeine causes stimulation.

I'm still not able to understand how is it a finding of an experiment.

Thanks
Kitty
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Caffeine, the stimulant in coffee, has been called “the most widely us 24 Aug 2022, 20:48
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KittyDoodles

I thought the assumption is "the ability of the compounds to compete at the receptors correlates with locomotion." Thus, this is how caffeine causes stimulation.

I'm still not able to understand how is it a finding of an experiment.
Show more

This problem follows GMAC's typical pattern: The more technical detail there is in the text, the LESS important it is for you to understand those details specifically.

In fact, all you really need to figure out the role of the quote is to notice the verb with which it's presented:
"..., they reported"

What, from a scientific experiment, would you report? You'd report the findings of the experiment. (You could e.g. list or mention assumptions made in the experimental design, but it wouldn't make any sense to say that you were 'reporting' assumptions.)


If you do comprehend what's stated in the quote, then you can notice that a statistical correlation is being reported ("the higher X is, the higher Y is as well").
Correlations come from data, which must be the results of the experiment (not its assumptions or anything else).
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Caffeine, the stimulant in coffee, has been called “the most widely us 16 Nov 2022, 21:49
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Q5 structural similarity(identical) vs structural relationship(between two objects, can be similar or different) got me wrong, how can one say both are same.
Q1 primary purpose: blank on that question, lost in such long RC... can anybody help how to reach the PP?
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Caffeine, the stimulant in coffee, has been called “the most widely us 23 Nov 2022, 11:13
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Question 5


hrusher
Q5 structural similarity(identical) vs structural relationship(between two objects, can be similar or different) got me wrong, how can one say both are same.
Show more
Regarding Q5, let's start by considering the following key points from the passage:

  • According to Snyder, caffeine "affects behavior by countering the activity in the human brain of...adenosine."
  • Adenosine normally creates its effect by "inhibiting the release of neurotransmitters."
  • Adenosine normally binds to receptors A1 and A2.
  • "Caffeine, which is structurally similar to adenosine, is able to bind to both types of receptors..." (i.e. A1 and A2).

Let's now consider answer choice (C):

Quote:
5. Snyder et al. suggest that caffeine’s ability to bind to A1 and A2 receptors can be at least partially attributed to which of the following?

(C) The structural similarity between caffeine and neurotransmitters
Show more
The passage does talk about a structural similarity. However, it tells us that caffeine is similar to adenosine, not too neurotransmitters. Notice adenosine inhibits the release of neurotransmitters, so adenosine itself is not a neurotransmitter. Eliminate (C).

Let's now consider (B):

Quote:
(B) The structural relationship between caffeine and adenosine
Show more
As you suggest, the word "structural relationship" doesn't necessarily mean similarity. It could mean similarity, or it could mean some other type of relationship.

That being said, the passage does suggest that caffeine's ability to bind to A1 and and A2 is related to its structural similarity to adenosine. And if two structures are similar, you could say they have a "structural relationship."

So while (B) doesn't specify that the structures are similar exactly, it's still a true statement: the structural relationship between caffeine and adenosine (i.e. in this case, the fact they have similar structures) helps explain why caffeine can bind A1 and A2. For that reason, (B) is correct.


Question 1


hrusher

Q1 primary purpose: blank on that question, lost in such long RC... can anybody help how to reach the PP?
Show more
For tips on identifying the primary purpose of this passage, check out this video, which analyzes this passage in detail and goes through several of the questions (including question 1). For general pointers on how to identify the primary purpose, check out our RC guide for beginners or this RC video playlist.

I hope that helps!
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Caffeine, the stimulant in coffee, has been called “the most widely us 18 Dec 2022, 07:48
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Sajjad1994
Please read the explanation in the post in the link below

https://gmatclub.com/forum/caffeine-the ... l#p2827944

Thank you!

jarbit
Hi Sajjad1994, can you help me with the question no 6? I picked D because I assumed that the highlighted passage talked about correlations and I rejected B here since it did not talk about any experiments specifically.

6. The author quotes Snyder et al.[highlighted] in lines 43–48 most probably in order to

(A) reveal some of the assumptions underlying their theory
(B) summarize a major finding of their experiments
(C) point out that their experiments were limited to the mouse
(D) indicate that their experiments resulted only in general correlations
(E) refute the objections made by supporters of the older theory
Show more

Sajjad1994
I would be so appreciative if you also perhaps have the Official Explanations (I do not see the exact code) for the following questions:

Which of the following, if true, would most weaken the theory proposed by Snyder et al?
(A) At very low concentrations in the human brain, both caffeine and theophylline tend to have depressive rather than stimulatory effects on human behavior.
(B) The ability of caffeine derivatives at very low concentrations to dislodge adenosine from its receptors in mouse brains correlates well with their ability to stimulate mouse locomotion at these low concentrations.
(C) The concentration of cyclic AMP in target neurons in the human brain that leads to increased neuron firing can be produced by several different phosphodiesterase inhibitors in addition to caffeine.
(D) The concentration of caffeine required to dislodge adenosine from its receptors in the human brain is much greater than the concentration that produces behavioral stimulation in humans.
(E) The concentration of IBMX required to dislodge adenosine from its receptors in mouse brains is much smaller than the concentration that stimulates locomotion in the mouse.


The passage suggests that Snyder et al believe that if the older theory concerning caffeine’s effects were correct, which of the following would have to be the case?
I. All neurotransmitters would increase the short-term concentration of cyclic AMP in target neurons.
II. Substances other than caffeine that inhibit the production of phosphodiesterase would be stimulants.
III. All concentration levels of caffeine that are high enough to produce stimulation would also inhibit the production of phosphodiesterase.
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only
(E) I, II, and III


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AbhishekDhanraJ72
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Caffeine, the stimulant in coffee, has been called “the most widely us 20 Mar 2023, 01:03
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AndrewN
Hello, adkikani. If you need to answer a question about binding, then you should look for the keyword bind in the passage, particularly because the frame of the question, as an EXCEPT, lets you know that you are looking for a detail. How about we approach the task, answer by answer?

surat
4. According to Snyder et al., all of the following compounds can bind to specific receptors in the brain EXCEPT

surat
(A) IBMX
Analysis: The last paragraph states that IBMX bound very well in the context of adenosine receptor binding and stimulation. You might be able to kill two birds with one stone here and cross off (C) as well, but if you were being extra careful, at least you could get rid of this answer choice.

surat
(B) caffeine
Analysis: Paragraph two states that Snyder et al. propose that caffeine, which is structurally similar to adenosine, is able to bind to both types of receptors. Yes, this is a proposal rather than a statement of fact, but look at the question again: According to Snyder et al. This answer cannot be argued against.

surat
(C) adenosine
Analysis: If the two previous analyses did not convince you that adenosine can bind to receptors in the brain, then I am not sure how many instances you need from the passage to convey the point. The first such instance is from the beginning of paragraph two: adenosine must first bind to specific receptors on neuronal membranes. Three strikes and you're out.

surat
(D) theophylline
Analysis: The highlighted portion of paragraph four draws attention to theophylline, which was one of the most effective compounds in both regards. Which regards, exactly? One of them is spelled out with an id est: the higher their capacity to bind at the receptors. Thus, theophylline is not our answer.

surat
(E) phosphodiesterase
Analysis: The process of elimination points to this odd one out, without even a check. However, in the interest of providing a full analysis, what does the passage say about phosphodiesterase? The appositive phrase attached to the word in paragraph three tells us: an enzyme that breaks down the chemical called cyclic AMP. The rest of the paragraph talks about this enzyme, but nowhere will you find the keyword bind.

I have said it before, and I will reiterate here: keep your approach simple. The more you delve into the semantics or possibilities of each answer choice, the harder the test is going to be for you. Stick to the surface.

- Andrew
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Please rectify your answer.

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Caffeine, the stimulant in coffee, has been called “the most widely us 04 Feb 2024, 05:11
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