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For some time scientists have believed that cholesterol pla
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27 Jan 2019, 10:51
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For some time scientists have believed that cholesterol plays a major role in heart disease because people with familial hypercholesterolemia, a genetic defect, have 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 familiar 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.
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17. 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
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18. Which of the following drugs, if developed, would most likely be an example of the kind of drug mentioned ?
(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
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19. 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?
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20. 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
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21. 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
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22. 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
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23. 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.
Re: For some time scientists have believed that cholesterol pla
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31 May 2020, 05:17
5
In people with familial hypercholesterolemia, there are no LDL receptors which remove LDL from blood. LDL contains cholesterol hence in these persons, rise in cholesterol level leads to increase in blood pressure. However, it is also found that in such persons, more LDLs are produced than in normal person. This passage seeks answer to this question Para 2 and 3 are about experiments involving Watanabe rabbits. These experiments highlighted dual role of receptors in preventing increase in cholesterol
17. In the passage, the author is primarily concerned with (B) raising a question and describing an important discovery that led to an answer Correct: 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?
18. Which of the following drugs, if developed, would most likely be an example of the kind of drug mentioned? (B) A drug that stimulates the production of LDL receptors on the liver correct- Para 3 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....
19. The passage supplies information to answer which of the following questions? (C) Where in the body are VLDL remnants degraded? Correct- Para 3- Normally, the majority of the VLDL remnants go to the liver where they bind to LDL receptors and are degraded
20. 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 Para 3- What scientists learned by studying the Watanabe rabbits is that the removal of the VLDL remnant requires the LDL receptor.
21. The development of drug treatments for some forms of familial hypercholesterolemia is regarded by the author as (E) highly probable correct- With this knowledge, scientists are now well on the way toward developing drugs
22. 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 Both A & B are incorrect trap answer (C) less useful than they actually were to scientists in the study of familial hypercholesterolemia in humans correct- Those rabbits with familial hypercholesterolemia, lacked LDL receptors. Thus, scientists could study these Watanabe rabbits to gain a better understanding of familial hypercholesterolemia in humans.
23. 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. Incorrect- This is exactly opposite. (B) The blood of Watanabe rabbits contains more VLDL remnants than does the blood of normal rabbits. Correct- In the Watanabe rabbit, due to a lack of LDL receptors on liver cells, the VLDL remnants remain in the blood (E) The blood of Watanabe rabbits contains fewer LDL's than does the blood of normal rabbits. Incorrect trap answer- Passage only mentions Watanabe rabbits don't have LDL receptors. It does not mention about LDL
Re: For some time scientists have believed that cholesterol pla
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22 Feb 2020, 10:42
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Expert Reply
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.
The above portions represent A.
E is wrong because is not a finding by scientists or a new discovery. It is just an observation. A fact.
The stem asks you they learned something new. E instead of observation in the entire story of LDL that we did know.
Re: For some time scientists have believed that cholesterol pla
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25 Feb 2020, 19:55
1
Could someone help with Q18 & Q23 ? below was my analysis on 18 & 23 Q18: Which of the following drugs, if developed, would most likely be an example of the kind of drug mentioned ?
(A) A drug that stimulates the production of VLDL remnants => shouldnt this be the answer, as we got to know from the passage that remnant VLDLs are converted to LDLs which can make up for the deficiency , due to which high levels of cholesterol is experienced (B) A drug that stimulates the production of LDL receptors on the liver => this option seem to cater to only the VLDL remnants and not counter the dearth of LDL cells
23. The passage implies that Watanabe rabbits differ from normal rabbits in which of the following ways? Doesnt option (E) "The blood of Watanabe rabbits contains fewer LDL's than does the blood of normal rabbits." makes sense here based on below passage
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.
While option B "(B) The blood of Watanabe rabbits contains more VLDL remnants than does the blood of normal rabbits.", also seems right.
Schools: Copenhagen Business School - Class of 2022
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Re: For some time scientists have believed that cholesterol pla
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17 Apr 2020, 13:05
1
For q23 I would say that this is the fundamental sentence.
""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.""
This sentence basically leads us to the fact that we had less LDLs than VLDLs (meaning we are sort of able to determine that we have an amplified number of VLDLs than in a normal rabbit).
Re: For some time scientists have believed that cholesterol pla
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17 Apr 2020, 15:04
1
bubidag wrote:
For q23 I would say that this is the fundamental sentence.
""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.""
This sentence basically leads us to the fact that we had less LDLs than VLDLs (meaning we are sort of able to determine that we have an amplified number of VLDLs than in a normal rabbit).
Please correct if wrong.
Yes, you are correct. Since watnabe rabbits have less LDL receptors than normal rabbits. This can be inferred that they contain more VLDL remnants than normal rabbits do.
Re: For some time scientists have believed that cholesterol pla
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06 Oct 2020, 12:48
More specifically how much time should one ideally take to complete a big book long passage consisting of 7 questions , thanks a lot for the previous reply though .