题干

      阅读下文,回答(1)~(5)题。

植物也有血型

      ①人们都知道动物有血液,且大多数颜色是鲜红的。但也有些动物的血液呈现出别种颜色,还有不同的血型。可你知道吗?从某种意义上讲,植物也有血液,那就是它的汁液。它们不仅有不同的颜色,并且令人称奇的是,植物也有血型!

      ②植物“血液”的颜色,有的是透明的,有的呈乳白色,有的与人血一样为鲜红色;有的呈流质状,有的很粘稠;有的香气扑鼻,有的臭味熏天。而植物也有血型,却是人们在一次偶然的机会中发现的。

      ③一天,一位日本妇女在家中死去,警察赶到现场,一时无法判断是自杀还是他杀,便进行血迹化验。经化验死者的血型为O型,可枕头上的血迹为AB型,遂怀疑是他杀。可是后来一直找不到凶手作案的佐证。于是有人提出,会不会枕头里的荞麦皮也有血型呢?经过化验,荞麦皮的血型果然为AB型。

      ④据科学家研究,蔬菜、水果也有血型,它们与人一样,也有A、B、O型的血型。经过研究发现,苹果、草莓、南瓜、山茶、辛夷等60种植物的血型为O型。在大约150种蔬菜、水果中,有血型的占19种。500余种植物种子中的60种有血型,其中,O型大约占一半,剩下的是B型或者是AB型,目前还没有发现有A型的。

      ⑤植物为什么会有血型呢?科学家研究证实,人和一些动物的红血球细胞膜表面有一种特殊的抗原物质,正是这种抗原物质不同的分子结构决定了血液的类型。而植物没有红色细胞,但它却有类似人体内附在红细胞表面的血型物质——血型糖。不同的血型糖便决定了不同的血型,这就是植物也有血型的奥秘所在。研究者还发现:植物的血型物质除了担当植物能量的储藏物外,由于本身粘度大,也担负着保护植物体的作用。

      ⑥科学家发现,在玉米、油菜和烟草等植物体中,含有类似于人体血红蛋白的基因。这表明植物也有造血功能!如果再把铁原子加入其中,就能够造出人体所需要的血红蛋白。血红蛋白是人体红细胞的重要组成部分,它易于与氧结合和分离,因此具有输送氧的功能。利用植物制造出人体所需要的血液,这种愿望如果能够成为现实,那么人类拥有的血库中的血就会取之不尽,而且安全性也会大大提高,不会携带艾滋病毒、肝炎病毒等人类血液中的有害物质。

(选自《课外阅读》2013年第3期)

上一题 下一题 0.0难度 选择题 更新时间:2014-03-06 02:15:26

答案(点此获取答案解析)

同类题5

阅读理解

    For some people, music is no fun at all. About four percent of the population is what scientists call “amusic”. People who are amusic are born without the ability to recognize or reproduce musical notes (音调). Amusic people often cannot tell the difference between two-songs. Amusics can only hear the difference between two notes if they are far apart on the musical scale.

    As a result, songs sound like noise to an amusic. Many amusics compare the sound of music to pieces of metal hitting each other. Life can be hard for amusics. Their ability to enjoy music sets them apart from others. It can be difficult for other people to identify with their condition. In fact, most people cannot begin to grasp what it feels like to be amusic. Just going to a restaurant or a shopping mall can be uncomfortable or even painful. That is why many amusics intentionally(故意地)stay away from places where there is music. However, this can result in withdrawal and social isolation. “I used to hate parties,” says Margaret, a seventy-year-old woman who only recently discovered that she was amusic. By studying people like Margaret, scientists arc finally learning bow to identify this unusual condition.

    Scientists say that the brains of amusics are different from the brains of people who can appreciate music. The difference is complex, and it doesn't involve defective hearing. Amusics can understand other nonmusical sounds well. They also have no problems understanding ordinary speech. Scientists compare amusics to people who just can't sec certain colors.

    Many amusics are happy when their condition is finally diagnosed. For years. Margaret felt embarrassed about her problem with music. Now she knows that she is not alone. There is a name for her condition. That makes it easier for her to explain. “When people invite me to a concert, I just say, 'No thanks. I'm amusic,'” says Margaret. “I just wish I had learned to say that when I was seventeen and not seventy.”