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简述光呼吸的意义。

答案

参考答案：

⑴回收碳素通过C2碳氧化环可回收乙醇酸中3/4的碳（2个乙醇酸转化1个PGA，释放1个CO2）。

⑵维持C3光合碳还原循环的运转在叶片气孔关闭或外界CO2浓度低时，光呼吸释放的CO2能被C3途径再利用，以维持光合碳还原环的运转。

⑶防止强光对光合机构的破坏作用在强光下，光反应中形成的同化力会超过CO2同化的需要，从而使叶绿体中NADPH/NADP、ATP/ADP的比值增高。同时由光激发的高能电子会传递给O2，形成的超氧阴离子自由基会对光合膜、光合器有伤害作用，而光呼吸却可消耗同化力与高能电子，降低超氧阴离子自由基的形成，从而保护叶绿体，免除或减少强光对光合机构的破坏。

单项选择题

病人证见神疲乏力，形寒肢冷，小使短少，腰重脚肿，舌质淡胖，苔薄白，脉沉迟而细。治疗最佳选用的方剂足

A．右归饮

B．金匮肾气丸

C．左归丸

D．四逆散

E．济生肾气丸
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单项选择题

The girls in this sixth grade class in East Palo Alto, California, all have the same access to computers as boys. But researchers say, by the time they get to high school, they are victims of what the researchers call a major new gender (性别) gap in technology. Janice Weinman of the American Association of University Women says, "Girls tend to be less comfortable than boys with the computer. They use it more for word processing rather than for problem solving, rather than to discover new ways in which to understand information."

The research on girls and computers is ______.
A. based on a few recent articles B. presented by one person
C. based on thousands of studies D. not considered well grounded

After re-examining a thousand studies, the American Association of University Women researchers found that girls make up only a small percentage of students in computer science classes. Girls consistently rate themselves significantly lower than boys in their ability and confidence in using computers. And they use computers less often than boys outside the classroom.An instructor of a computer lab says he’s already noticed some differences. Charles Cheadle of Cesar Chavez School says, "Boys are not so afraid they might do something that will harm the computer, whereas girls are afraid they might break it somehow."
Six years ago, the software company Purple Moon noticed that girls’ computer usage was falling behind boys. Karen Gould says, "The number one reason girls told us they don’t like computer games is not that they’re too violent, or too competitive. Girls just said they’re incredibly boring."
Purple Moon says it found what girls want, characters they can relate to and story lines relative to what’s going on in their own lives. Karen Gould of Purple Moon Software says, "What we definitely found from girls is that there is no intrinsic (固有的) reason why they wouldn’t want to play on a computer; it was just a content thing."
The sponsor of the study says it all boils down to this: the technology gender gap that separates the girls from the boys must be closed if women are to compete effectively with men in the 21st century.
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