题干

对某动物细胞进行荧光标记实验,如下图所示,其基本过程:
①用某种荧光染料标记该动物细胞,细胞表面出现荧光斑点;
②用激光束照射该细胞表面的某一区域,该区域荧光消失;
③停止激光束照射一段时间后,该区域的荧光逐渐恢复,即又出现了斑点。

上述实验能说明的是:(   )

A:细胞膜具有流动性

B:荧光染料无法与细胞膜组成成分结合

C:根据荧光恢复的速率可推算出物质跨膜运输的速率

D:细胞膜具有选择透过性

上一题 下一题 0.0难度 选择题 更新时间:2015-09-24 02:40:44

答案(点此获取答案解析)

A

同类题5

阅读下面短文,从短文后各题所给的A、B、C、D四个选项中,选出最佳选项。

    Gwondo was a trainer of dogs. He would go out every day with his dogs, to1 them how to catch animals so all his tribe(部落) could eat.

    Wherever Gwondo went, his tribe could see him away in the distance  2 his white hair would shine in the sunlight. The tribe 3would say to their children, "See, there is Gwondo and his dogs, searching for 4 for us all. " Gwondo went out hunting every day and always came 5 with much food. And all were very happy.

    Now Gwondo grew 6 and as all humans do, one day he died. The tribe felt sad and cried many days and many nights 7 one day the elders called to their children, " You have cried enough for Gwondo. Now it is time to 8 living. Go down to the beach and be happy."

    The children ran down to the beach and looked out to sea. 9, they all looked at each other, then turned and ran back to their elders, 10, "Come quickly. Gwondo, he is back with us. He is out in the sea. "The elders hurried to the 11 and said, "Yes! It is Gwondo back! He is now a dolphin and lives in the sea. "

    Now whenever you see 12 dolphins in the sea, look for the big old dolphin. You will know him because he has a large white fin on 13 back. He is Gwondo and he is training the young dolphins to chase(追逐) 14 close to the beach so that his tribe can catch them.

     Gwondo is known to all the tribes 15 the east coast of Australia. They call him their sea dog.