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For some time scientists have believed that cholesterol plays a major

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For some time scientists have believed that cholesterol plays a major  [#permalink]

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New post Updated on: 02 May 2020, 08:39
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Project RC Butler 2020 - Participate and win GMAT Club Tests.
Passage # 63, Date: 02-May-2020
This post is a part of Project RC Butler 2020. Click here for Details


For some time scientists have believed that cholesterol plays a major role in heart disease because people with familial hypercholesterolemia, a genetic defect, have Line six to eight times the normal level of cholesterol in their blood and they invariably develop heart disease. These people lack cell-surface receptors for low-density lipoproteins (LDL's), which are the fundamental carriers of blood cholesterol to the body cells that use cholesterol. Without an adequate number of cell-surface receptors to remove LDL's from the blood, the cholesterol-carrying LDL's remain in the blood, increasing blood cholesterol levels. Scientists also noticed that people with familial hypercholesterolemia appear to produce more LDL's than normal individuals. How, scientists wondered, could a genetic mutation that causes a slow-down in the removal of LDL's from the blood also result in an increase in the synthesis of this cholesterol-carrying protein?

Since scientists could not experiment on human body tissue, their knowledge of familial hypercholesterolemia was severely limited. However, a breakthrough came in the laboratories of Yoshio Watanabe of Kobe University in Japan in 1980. Watanabe noticed that a male rabbit in his colony had ten times the normal concentration of cholesterol in its blood. By appropriate breeding, Watanabe obtained a strain of rabbits that had very high cholesterol levels. These rabbits spontaneously developed heart disease. To his surprise, Watanabe further found that the rabbits, like humans with familial hypercholesterolemia, lacked LDL receptors. Thus, scientists could study these Watanabe rabbits to gain a better understanding of familial hypercholesterolemia in humans.

Prior to the breakthrough at Kobe University, it was known that LDL's are secreted from the liver in the form of a precursor, called very low-density lipoproteins (VLDL's), which carry triglycerides as well as relatively small amounts of cholesterol. The triglycerides are removed from the VLDL's by fatty and other tissues. What remains is a remnant particle that must be removed from the blood. What scientists learned by studying the Watanabe rabbits is that the removal of the VLDL remnant requires the LDL receptor. Normally, the majority of the VLDL remnants go to the liver where they bind to LDL receptors and are degraded. In the Watanabe rabbit, due to a lack of LDL receptors on liver cells, the VLDL remnants remain in the blood and are eventually converted to LDL's. The LDL receptors thus have a dual effect in controlling LDL levels. They are necessary to prevent over synthesis of LDL's from VLDL remnants and they are necessary for the normal removal of LDL's from the blood. With this knowledge, scientists are now well on the way toward developing drugs that dramatically lower cholesterol levels in people afflicted with certain forms of familial hypercholesterolemia.

Spoiler: :: OA
B

In the passage, the author is primarily concerned with

(A) presenting a hypothesis and describing compelling evidence in support of it
(B) raising a question and describing an important discovery that led to an answer
(C) showing that a certain genetically caused disease can be treated effectively with drugs
(D) explaining what causes the genetic mutation that leads to heart disease
(E) discussing the importance of research on animals for the study of human disease


Spoiler: :: OA
B

Which of the following drugs, if developed, would most likely be an example of the kind of drug mentioned in line 53 ?

(A) A drug that stimulates the production of VLDL remnants
(B) A drug that stimulates the production of LDL receptors on the liver
(C) A drug that stimulates the production of an enzyme needed for cholesterol production
(D) A drug that suppresses the production of body cells that use cholesterol
(E) A drug that prevents triglycerides from attaching to VLDL's


Spoiler: :: OA
C

The passage supplies information to answer which of the following questions?

(A) Which body cells are the primary users of cholesterol?
(B) How did scientists discover that LDL's are secreted from the liver in the form of a precursor?
(C) Where in the body are VLDL remnants degraded?
(D) Which body tissues produce triglycerides?
(E) What techniques are used to determine the presence or absence of cell-surface receptors?


Spoiler: :: OA
A

According to the passage, by studying the Watanabe rabbits scientists learned that

(A) VLDL remnants are removed from the blood by LDL receptors in the liver
(B) LDL's are secreted from the liver in the form of precursors called VLDL's
(C) VLDL remnant particles contain small amounts of cholesterol
(D) triglycerides are removed from VLDL's by fatty tissues
(E) LDL receptors remove LDL's from the blood


Spoiler: :: OA
E

The development of drug treatments for some forms of familial hypercholesterolemia is regarded by the author as

(A) possible, but not very important
(B) interesting, but too costly to be practical
(C) promising, but many years off
(D) extremely unlikely
(E) highly probable


Spoiler: :: OA
C

The passage implies that if the Watanabe rabbits had had as many LDL receptors on their livers as do normal rabbits, the Watanabe rabbits would have been

(A) less likely than normal rabbits to develop heart disease
(B) less likely than normal rabbits to develop high concentrations of cholesterol in their blood
(C) less useful than they actually were to scientists in the study of familial hypercholesterolemia in humans
(D) unable to secrete VLDL's from their livers
(E) immune to drugs that lower cholesterol levels in people with certain forms of familial hypercholesterolemia


Spoiler: :: OA
B

The passage implies that Watanabe rabbits differ from normal rabbits in which of the following ways?

(A) Watanabe rabbits have more LDL receptors than do normal rabbits.
(B) The blood of Watanabe rabbits contains more VLDL remnants than does the blood of normal rabbits.
(C) Watanabe rabbits have fewer fatty tissues than do normal rabbits.
(D) Watanabe rabbits secrete lower levels of VLDL's than do normal rabbits.
(E) The blood of Watanabe rabbits contains fewer LDL's than does the blood of normal rabbits.


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Originally posted by carcass on 27 Jan 2019, 10:55.
Last edited by SajjadAhmad on 02 May 2020, 08:39, edited 2 times in total.
Updated - Complete topic (1106).
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Re: For some time scientists have believed that cholesterol plays a major  [#permalink]

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Re: For some time scientists have believed that cholesterol plays a major  [#permalink]

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New post 01 Mar 2019, 06:21
1
6 correct 1 wrong
explanation for first 6 ques


In the passage, the author is primarily concerned with

(A) presenting a hypothesis and describing compelling evidence in support of it ( No evidence , that is actually a research , so ruled out )
(B) raising a question and describing an important discovery that led to an answer ( clearly passage 1 starts with an ques , and rest follows an important discovery with the help of research conducted .
(C) showing that a certain genetically caused disease can be treated effectively with drugs . (No talking about treatment , treatment is talked only in last part )
(D) explaining what causes the genetic mutation that leads to heart disease . (Genetic mutation , NO , ruled out )
(E) discussing the importance of research on animals for the study of human disease ( not discussing about research on animals )

Which of the following drugs, if developed, would most likely be an example of the kind of drug mentioned in line 53 ?

(A) A drug that stimulates the production of VLDL remnants
(B) A drug that stimulates the production of LDL receptors on the liver In the Watanabe rabbit, due to a lack of LDL receptors on liver cells, the VLDL remnants remain in the blood and are eventually converted to LDL's. The LDL receptors thus have a dual effect in controlling LDL levels. They are necessary to prevent over synthesis of LDL's from VLDL remnants and they are necessary for the normal removal of LDL's from the blood. hence B
(C) A drug that stimulates the production of an enzyme needed for cholesterol production
(D) A drug that suppresses the production of body cells that use cholesterol
(E) A drug that prevents triglycerides from attaching to VLDL's

The passage supplies information to answer which of the following questions?

(A) Which body cells are the primary users of cholesterol?
(B) How did scientists discover that LDL's are secreted from the liver in the form of a precursor?
(C) Where in the body are VLDL remnants degraded? The triglycerides are removed from the VLDL's by fatty and other tissues. What remains is a remnant particle that must be removed from the blood. What scientists learned by studying the Watanabe rabbits is that the removal of the VLDL remnant requires the LDL receptor. Normally, the majority of the VLDL remnants go to the liver where they bind to LDL receptors and are degraded.
(D) Which body tissues produce triglycerides?
(E) What techniques are used to determine the presence or absence of cell-surface receptors?

According to the passage, by studying the Watanabe rabbits scientists learned that

(A) VLDL remnants are removed from the blood by LDL receptors in the liver In the Watanabe rabbit, due to a lack of LDL receptors on liver cells, the VLDL remnants remain in the blood and are eventually converted to LDL's. The LDL receptors thus have a dual effect in controlling LDL levels. They are necessary to prevent over synthesis of LDL's from VLDL remnants and they are necessary for the normal removal of LDL's from the blood
(B) LDL's are secreted from the liver in the form of precursors called VLDL's
(C) VLDL remnant particles contain small amounts of cholesterol
(D) triglycerides are removed from VLDL's by fatty tissues
(E) LDL receptors remove LDL's from the blood

The development of drug treatments for some forms of familial hypercholesterolemia is regarded by the author as

(A) possible, but not very important
(B) interesting, but too costly to be practical
(C) promising, but many years off
(D) extremely unlikely
(E) highly probable easy one ,With this knowledge, scientists are now well on the way toward developing drugs that dramatically lower cholesterol levels in people afflicted with certain forms of familial hypercholesterolemia.

The passage implies that if the Watanabe rabbits had had as many LDL receptors on their livers as do normal rabbits, the Watanabe rabbits would have been

(A) less likely than normal rabbits to develop heart disease
(B) less likely than normal rabbits to develop high concentrations of cholesterol in their blood
(C) less useful than they actually were to scientists in the study of familial hypercholesterolemia in humans Watanabe obtained a strain of rabbits that had very high cholesterol levels. These rabbits spontaneously developed heart disease. To his surprise, Watanabe further found that the rabbits, like humans with familial hypercholesterolemia, lacked LDL receptors. Thus, scientists could study these Watanabe rabbits to gain a better understanding of familial hypercholesterolemia in humans.
(D) unable to secrete VLDL's from their livers
(E) immune to drugs that lower cholesterol levels in people with certain forms of familial hypercholesterolemia
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Re: For some time scientists have believed that cholesterol plays a major  [#permalink]

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New post 02 May 2020, 08:40
+1 Kudos to posts containing answer explanation of all questions
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Re: For some time scientists have believed that cholesterol plays a major  [#permalink]

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New post 02 May 2020, 21:31
1
1. In the passage, the author is primarily concerned with
Passage analysis: mechanism of cholesterol carrying is explained and a question is raised (para1). A breakthrough is discussed (para2). Finally, how this breakthrough helped to come up with a solution

(A) presenting a hypothesis and describing compelling evidence in support of it - not correct, no hypothesis is discussed

(B) raising a question and describing an important discovery that led to an answer - correct, in line with our passage analysis

(C) showing that a certain genetically caused disease can be treated effectively with drugs - not correct, no discussion of effective treatment

(D) explaining what causes the genetic mutation that leads to heart disease - not correct, this question is raised in para1

(E) discussing the importance of research on animals for the study of human disease - not correct, author didn't stress on the importance of research, however, a breakthrough from research on animals led to the better understanding of familial hyp..
_______________________________________________________________________________________________________________________________________________
2. Which of the following drugs, if developed, would most likely be an example of the kind of drug mentioned in line 53 ?

(A) A drug that stimulates the production of VLDL remnants - not correct, opposite

(B) A drug that stimulates the production of LDL receptors on the liver - correct, passage says 'The LDL receptors thus have a dual effect in controlling LDL levels. They are necessary to prevent over synthesis of LDL's from VLDL remnants and they are necessary for the normal removal of LDL's from the blood'

(C) A drug that stimulates the production of an enzyme needed for cholesterol production - not correct, opposite

(D) A drug that suppresses the production of body cells that use cholesterol - not correct, no discussion of body cells suppression

(E) A drug that prevents triglycerides from attaching to VLDL's - not correct, no discussion on preventing triglycerides to solve cholesterol problem
______________________________________________________________________________________________________________________________________
3. The passage supplies information to answer which of the following questions?

(A) Which body cells are the primary users of cholesterol? - not correct, no discussion of type of body cells that are primary users of cholesterol

(B) How did scientists discover that LDL's are secreted from the liver in the form of a precursor? - not correct, it was already known - 'it was known that LDL's are secreted from the liver in the form of a precursor'[/i]

(C) Where in the body are VLDL remnants degraded? - correct, passage says 'Normally, the majority of the VLDL remnants go to the liver where they bind to LDL receptors and are degraded'

(D) Which body tissues produce triglycerides? - [i]not correct, no discussion of body tissues


(E) What techniques are used to determine the presence or absence of cell-surface receptors? - not correct, no discussion of techniques
________________________________________________________________________________________________________________________________
4. According to the passage, by studying the Watanabe rabbits scientists learned that

(A) VLDL remnants are removed from the blood by LDL receptors in the liver - correct, passage says 'What scientists learned by studying the Watanabe rabbits is that the removal of the VLDL remnant requires the LDL receptor. Normally, the majority of the VLDL remnants go to the liver where they bind to LDL receptors and are degraded'

(B) LDL's are secreted from the liver in the form of precursors called VLDL's - not correct, it was known already

(C) VLDL remnant particles contain small amounts of cholesterol - not correct, it was known already

(D) triglycerides are removed from VLDL's by fatty tissues - not correct, it was known already

(E) LDL receptors remove LDL's from the blood - not correct, LDL receptors remove VLDL remnants, not LDL. However, I didn't pay close attention to the 'LDL's', and I thought of it as 'VLDL's'. So, I choose this choice
__________________________________________________________________________________________________________________
5. The development of drug treatments for some forms of familial hypercholesterolemia is regarded by the author as

(A) possible, but not very important - not correct, didn't say 'not very important'

(B) interesting, but too costly to be practical - not correct, no discussion of cost

(C) promising, but many years off - not correct, no discussion of time to develop this drug

(D) extremely unlikely - not correct, opposite

(E) highly probable - correct, passage says 'well on the way toward developing drugs that dramatically lower cholesterol levels'
_____________________________________________________________________________________________________________________________
6. The passage implies that if the Watanabe rabbits had had as many LDL receptors on their livers as do normal rabbits, the Watanabe rabbits would have been

(A) less likely than normal rabbits to develop heart disease - not correct, if LDL receptors are same then the likelihood to develop heart disease also remains same

(B) less likely than normal rabbits to develop high concentrations of cholesterol in their blood - not correct, if LDL receptors are same then the likelihood to develop high concentrations of cholesterol also remains same

(C) less useful than they actually were to scientists in the study of familial hypercholesterolemia in humans - correct, if there was no change in LDL receptors in Watanabe's rabbits, he would not have found his breakthrough

(D) unable to secrete VLDL's from their livers - not correct, secretion rate would be same

(E) immune to drugs that lower cholesterol levels in people with certain forms of familial hypercholesterolemia - not correct, no discussion of immunity to drugs about these rabbits
___________________________________________________________________________________________________________________________
7. The passage implies that Watanabe rabbits differ from normal rabbits in which of the following ways?

(A) Watanabe rabbits have more LDL receptors than do normal rabbits. - not correct, opposite - 'Watanabe further found that the rabbits, like humans with familial hypercholesterolemia, lacked LDL receptors'

(B) The blood of Watanabe rabbits contains more VLDL remnants than does the blood of normal rabbits. - correct, passage says 'In the Watanabe rabbit, due to a lack of LDL receptors on liver cells, the VLDL remnants remain in the blood'

(C) Watanabe rabbits have fewer fatty tissues than do normal rabbits. - not correct, no comparison of fatty tissues

(D) Watanabe rabbits secrete lower levels of VLDL's than do normal rabbits. - not correct, no comparison of VLDL levels, secretion of VLDL was a just known fact

(E) The blood of Watanabe rabbits contains fewer LDL's than does the blood of normal rabbits. - not correct, para2 says 'Watanabe further found that the rabbits lacked LDL receptors', but I didn't pay attention to this detail and chose this choice. LDL receptors are different from LDL itself.
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Re: For some time scientists have believed that cholesterol plays a major  [#permalink]

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New post 04 May 2020, 03:44
SajjadAhmad

Can you pls explain why A is incorrect in Q1?

Also in Q4, why is E not the answer
The passage states "The LDL receptors thus have a dual effect in controlling LDL levels. They are necessary to prevent over synthesis of LDL's from VLDL remnants and they are necessary for the normal removal of LDL's from the blood"

Thanks in advance!
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Re: For some time scientists have believed that cholesterol plays a major  [#permalink]

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New post 05 May 2020, 10:21
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GDT wrote:
SajjadAhmad

Can you pls explain why A is incorrect in Q1?

Also in Q4, why is E not the answer
The passage states "The LDL receptors thus have a dual effect in controlling LDL levels. They are necessary to prevent over synthesis of LDL's from VLDL remnants and they are necessary for the normal removal of LDL's from the blood"

Thanks in advance!


Hello GDT

Answer options A and B are the two closed here, to get this question correct you just have to differentiate between the presenting a hypothesis and raising a question. When Authors present a hypothesis they did some analysis of facts Before presenting the issue, when they straight forward starts with the issue they raise a question. There is no home work here by the author before raising the issue, rather he/she provide the evidence once the raised the issue.

To get the answer of question number four read the lines 9-11 of the last paragraph

the majority of the VLDL remnants go to the liver where they bind to LDL receptors and are degraded. In the Watanabe rabbit, due to a lack of LDL receptors on liver cells

It leads to the answer.
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Re: For some time scientists have believed that cholesterol plays a major  [#permalink]

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New post 10 May 2020, 04:22
7:03 mins total including reading the passage. 6/7 correct
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Re: For some time scientists have believed that cholesterol plays a major   [#permalink] 10 May 2020, 04:22

For some time scientists have believed that cholesterol plays a major

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