首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
医学
Cholesterol plays a key role in the development of embryo cells, biologists have discovered. They say that this much maligned fa
Cholesterol plays a key role in the development of embryo cells, biologists have discovered. They say that this much maligned fa
admin
2014-01-15
54
问题
Cholesterol plays a key role in the development of embryo cells, biologists have discovered. They say that this much maligned fatty molecule, best known for its links to heart disease, helps to position a family of "controller" proteins that tell embryo cells how they should form.
In laboratory studies on fruit flies and mice, Phil Beachy and his colleagues at Johns Hopkins University in Baltimore looked at members of a family of controller proteins known as Hedgehog. Fruit fly embryos that lack the genes for these proteins develop a spiky appearance — hence the name. Biologists already know that Hedgehog proteins help to direct the development of embryo cells by delivering signals at the cell surface. The proteins only deliver their signals when they split in two, and one half binds to a lipid, a fatty molecule. Beachy’ s team discovered that this lipid is cholesterol.
In previous test-tube experiments, scientists have found that the concentration and distribution of Hedgehog proteins on the surface of embryo cells can be critical in determining their fate. For example, cells taken from the embryonic nervous system become motor neurons when exposed to low concentrations of Hedgehog proteins, while at high concentrations they turn into structural cells known as floor plates. Until now, however, no one knew what determined the concentration of the proteins on the surface of cells in the embryo.
Beachy’ s findings suggest that cholesterol’ s role is to allow the signaling proteins to enter cells. Since the lipid molecule is water-hating or hydrophobic, the researchers argue, it may act as a key, allowing the Hedgehog proteins to move through the hydrophobic membranes of target cells, or to stick to them. The results appear in the current issue of Science.
Researchers already know that cholesterol does some important jobs: for example, it is involved in the production of hormones and is vital for fertility and for the healthy membrane structure of cells. Beachy’ s latest results show that cholesterol is also needed for embryonic development. They also help to explain a long-known but mysterious finding that pregnant rats given drugs that block the manufacture of cholesterol produce deformed fetuses.
Gail Martin, a developmental biologist at the University of California, San Francisco, describes the findings as "exciting". They may also have wider implications, she says: it is likely that cholesterol’ s action is needed more generally for signaling between cells.
Beachy too believes that the findings may have "strong connections for human biology". For example, they throw light on a birth disorder that has been linked to the mother’ s inability to make cholesterol. This disorder, Smith-Lemli-Opitz syndrome, affects about 1 in 9000 newborn babies, causing defects such as small head size.
What, according to Beachy, determines the cholesterol’ s role is______.
选项
A、Hedgehog proteins
B、its hydrophobic nature
C、its ability to send signals
D、the hydrophobic membranes of embryo cells
答案
B
解析
本题要求“根据Beachy的观点”进行推断。从原文第四段的前两句(Beachy’sfindings suggest that cholesterol’s role is to allow the signaling proteins to enter cells.Sincethe lipid molecule is water-halting or hydrophobic,the researchers argue,It may act as a key,allowing the Hedgehog proteins to move through the hydrophobic membranes of…)中可以看出决定胆固醇作用的关键就在于其疏水性(hydrophobic nature or water-halting nature),所以正确答案为B。
转载请注明原文地址:https://kaotiyun.com/show/jbT3777K
本试题收录于:
医学博士外语题库考研分类
0
医学博士外语
考研
相关试题推荐
High-speedlivinghasbecomeafactoflife,andthefranticpaceistakingitstoll,accordingtosciencewriterJamesGleick.
High-speedlivinghasbecomeafactoflife,andthefranticpaceistakingitstoll,accordingtosciencewriterJamesGleick.
Physicsandchemistryhavefurnishedthetechniquesforbiologiststotaketheexplorationoflifetoitslogicalconclusion.Th
Physicsandchemistryhavefurnishedthetechniquesforbiologiststotaketheexplorationoflifetoitslogicalconclusion.Th
ManyCanadiansenjoytheluxuryofalargeamountoflivingspace.Canadaisvast,andthehomesarelargeaccordingtothestan
ManyCanadiansenjoytheluxuryofalargeamountoflivingspace.Canadaisvast,andthehomesarelargeaccordingtothestan
Thebiosphereisthenamebiologistsgivetothesortofskinonthesurfaceofthisplanetthatisinhabitablebylivingorgani
随机试题
根据新的任务,人有意识地把注意从一种活动和对象指向另一种活动和对象,是注意的哪一种品质【】
患者,女,25岁。低热2周。查体:气管不偏,右侧胸部呼吸运动减弱,叩诊呈浊音,肺泡呼吸音减低,可闻及湿啰音,左肺未见异常。根据患者的右侧胸部体征,可诊断为
关于CT图像重建技术的叙述,错误的是
下列细菌既为尿路感染最常见的病原菌,又可产ESBL的是
使用面弓的目的是
下列主体可作为保证人的是()。
良好的班集体具有哪些教育作用?
在标准ASCII编码表中,数字码、小写英文字母和大写英文字母的前后次序是
"Everythinghappensforthebest",mymothersaid(31)Ifaceddisappointment."Ifyoucarryon,onedaysomethinggoodwill(32
WaterSports水上运动Thehistoryofman’sinvolvementwithwatersports/stretchesbackbeforehistorywaswrittendown./Iti
最新回复
(
0
)