题目内容
6.Everyone is familiar with white fat,which serves as an energy warehouse.Many mammals also have brown fat,which has the unique ability to produce heat.Brown fat is sometimes mistaken for a type of gland (腺),which it resembles more than white fat.It varies in color from dark red to tan.When the animal is exposed to a cold environment,the color darkens.In contrast to white fat,brown fat has numerous nerves which provide sympathetic stimulation (刺激) to the fat cells.
Brown fat is most noticeable in newborn animals,wrapped round the central organs to keep them warm.In humaninfantsit occupies up to 5% of body weight,then declines gradually.Certain quantities of brown fat can be discovered in adult humans,especially when they are exposed to cold temperatures.Most of brown fat in adults is located in the lower neck.
Exposure to cold leads to sympathetic stimulation of brown fat cell.As in white fat,sympathetic stimulation promotes hydrolysis (水解) of triglyceride (甘油三酸脂),with release of fatty acids.In contrast to other cells,including white fat cells,brown fat cells express UCP1,which gives the cell's mitochondria (线粒体) an ability to produce heat rather than ATP.Within brown fat cells,most fatty acids are immediately combined with oxygen in mitochondria and a large amount of heat is produced.
There is only about 50g of brown fat in the neck region and it switches on and off throughout the day as it's exposed to different temperatures or if you exercise or eat.But this capacity is much greater in young children compared with adolescents and adults.
The challenge is now to use the knowledge to find out what might switch on brown fat.If it is switched on,we can benefit from it.Brown fat produces lots of heat by burning calories.Unlike white fat,brown fat does not expand our ageing waistlines.And that's why the race is on to find out more about brown fat,and how humans could use it to our advantage,though we would waste energy unnecessarily,and we would sweat a lot and forever be opening windows.
59.We can learn from the passage that brown fatA.
A.becomes less in amount with age
B.proves less active in low temperatures
C.exists nowhere but in the lower neck
D.has nothing in common with white fat
60.The underlined word"infants"in Paragraph 3means"D".
A.cells
B.organs
C.bodies
D.babies
61.We take special interest in brown fat mainly because it helps usD.
A.save energy
B.develop power
C.keep warm
D.keep our figure.
分析 这篇短文详细讲述了棕色脂肪对人体的作用.
解答 59-61 ADD
59 A 考查主旨归纳题.A.becomes less in amount with age随着年龄的增长数量变得更少;B.proves less active in low temperatures证明在低温不活跃;C.exists nowhere but in the lower neck只存在于较低的脖子处;D.has nothing in common with white fat和白色脂肪没有什么共同之处.根据倒数第二段But this capacity is much greater in young children compared with adolescents and adults.的描述我们可以了解到棕色脂肪随着年龄的增长会越来越少.故选A.
60 D 考查词义猜测题.A.cells 细胞;B.organs 器官;C.bodies 身体;D.babies 婴儿.句意:在人类婴儿中,它占据了人类体重的百分之五.故选D.
61 D A.save energy节约能源;B.develop power发展能力;C.keep warm保暖;D.keep our figure保持我们的形体.根据全文和最后一段Unlike white fat,brown fat does not expand our ageing waistlines的描述可知我们对棕色脂肪表现出特殊的兴趣主要因为它有助于我们保持我们的体型.故选D.
点评 做阅读理解时要快速的浏览全文,把握文章主旨大意,带着问题回到原文,寻找细节或概括相应的答案,最后要理清作者写作思路.

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