题干

整合素是细胞表面受体的主要家族。对细胞和细胞外基质的黏附起介导作用。整合素由α、β两条链构成,α链由1420个氨基酸构成,β链由840个氨基酸构成。下列有关整合素的叙述错误的是(      )

A:整合素组成糖蛋白,与细胞识别有关

B:控制整合素合成的基因中至少有6780个嘧啶碱基

C:整合素水解形成氨基酸,至少消耗2258个水分子

D:整合素的功能主要由两条链中氨基酸的种类决定

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D

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    There are many differences between country life and city life in many ways. One person even does different things in the two places.

    Julia lived in the countryside, but one year she decided to visit the capital city to do some shopping and to see the sights. She stayed at a hotel near the central market. She had seldom been to the city before, and was very excited about what she would find.

    On the first morning of her visit, as she walked from the hotel to the market, she passed a beggar(乞丐). He was holding up a notice, which said, “Blind from birth. Please give generously(慷慨地).”

    Julia felt sorry for the blind beggar and she bent down and put a dollar coin into his bowl. “Thank you.” he said.

    The same thing happened again the following day.

    On the third day, however, Julia did not have a dollar coin. She had only fifty cents, so she dropped this into the beggar's bowl.

    “What have I done wrong?” the beggar said, “Why are you so stingy today? ”

    Julia was very surprised at what the beggar said. “How do you know I haven't given you a dollar?” she said, “If you're blind you can't know what coin I put into your bowl.”

    “Ah, ” explained the beggar, “The truth is that I'm not blind. I'm just looking after this place for the regular beggar while he's on holiday.”

    “On holiday?” Julia said, “And what exactly does your blind friend do on holiday?”

    “He goes into the countryside,” the man said, “and takes photographs. He's a very good photographer.”