选课中心
7099人选课
GRE公开讲座
0元
GMAT公开讲座
0元
一对一体验课
99元
GRE模考网站
10000人
托福TPO模考网站HOT
39209人预约
GRE辅导课程
17537 人
GMAT辅导课程
17537 人
托福辅导课程
17537 人
【定制】1v1
私人订制
资料下载
考前冲刺
扫码关注掌握一手留学资讯
回复XDF免费领
水平测试和备考资料
扫码关注公众号
GRE阅读:家族性高胆固醇血症
For some time scientists have believed that cholesterol plays a major role in heart disease because people with familial hypercholesterolemia (hypercholesterolemia: n.[医]血胆脂醇过多), 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 familial hypercholesterolemia appear to produce more LDL’s than normal individuals. How, scientists wondered, could a genetic mutation that causes a slowdown 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 (triglyceride: n.[化]甘油三酸酯) 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 oversynthesis 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.
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(B)
(E) discussing the importance of research on animals for the study of human disease
18. 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(B)
(E) A drug that prevents triglycerides from attaching to VLDL’s
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?(C)
(E) What techniques are used to determine the presence or absence of cell-surface receptors?
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(A)
(E) LDL receptors remove LDL’s from the blood
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)
(E) highly probable
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(C)
(E) immune to drugs that lower cholesterol levels in people with certain forms of familial hypercholesterolemia
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.(B)
(E) The blood of Watanabe rabbits contains fewer LDL’s than does the blood of normal rabbits.
2月GRE公开课,助力GRE备考-1元抢报!
资料下载
GRE佛脚2024增补包含最新热词与六选二整理
发布时间:2022-06-06添加新东方在线美研助教号
回复【资料】获取
GRE-PPO模考完整套题+解析资料下载
发布时间:2022-06-06添加新东方在线美研助教号
回复【资料】获取
GRE佛脚词汇表网络版资料下载
发布时间:2022-05-21添加新东方在线美研助教号
回复【资料】获取
2024GRE佛脚填空机经系列资料下载
发布时间:2022-04-15添加新东方在线美研助教号
回复【资料】获取
2024GRE佛脚阅读系列资料下载
发布时间:2022-04-15添加新东方在线美研助教号
回复【资料】获取
2024杨鹏阅读难句(GMAT+GRE)教程资料下载
发布时间:2022-04-15添加新东方在线美研助教号
回复【资料】获取
GRE PPO模考完整练习题(答案)
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
GRE写作题库解析【Issue/Argument】
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
GRE阅读机经及官方真题资料练习
发布时间:2019-12-10关注新东方在线美研订阅号
回复【GRE】获取
GRE填空机经佛脚系列资料持续更新…
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
GRE佛脚词汇修订版PDF电子版下载
发布时间:2019-12-10添加新东方在线美研助教号
回复【资料】获取
【提升英语必看】英语记录片/演讲/美剧合集
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
《华尔街日报》、《纽约时报》英文报刊合集
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
【必看】美国研究生申请注意事项
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
美国研究生录取分数&截止日期信息汇总
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
2020美国研究生热门专业院校排名
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
GRE模考套题、机经汇总
发布时间:2019-11-27添加新东方在线美研助教号
回复【资料】获取
添加美研助教号,
回复【GRE】获取备考必看资料包
推荐阅读
更多>>为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读的命题规则,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读的排除法,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GRE
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读高分备考攻略,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读的做题思路,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读考试的相关技巧,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读合理分配好时间,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读考试的心态,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读考试的常见题型,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读长难句的语法介绍,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方
为了帮助大家高效备考GRE,新东方在线GRE频道为大家带来GRE阅读规律的介绍,希望对大家GRE备考有所帮助。更多精彩尽请关注新东方在线GR
添加美研助教号,
回复【GRE】获取备考必看资料包
资料下载
更多>>添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
关注新东方在线美研订阅号
回复【GRE】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
添加新东方在线美研助教号
回复【资料】获取
阅读排行榜
相关内容