题目

下列关于生物膜结构及其功能的叙述，正确的是A. 分泌蛋白的运输和分泌过程体现了生物膜的选择透过性B. 构成生物膜的磷脂分子和大多数蛋白质分子都可以运动C. 用蛋白酶处理生物膜可改变其组成，但不改变其通透性D. 内质网和高尔基体膜上附着核糖体，有利于对肽链的加工 答案：【答案】B【解析】本题旨在考查生物膜结构及功能，磷脂双分子层是轻油般的流体，具有流动性，生物膜中的大多数蛋白质分子也是可以运动的；细胞膜控制物质进出细胞，具有选择透过性。分泌蛋白的运输和分泌过程体现了生物膜结构的流动性，A错误； 构成生物膜的磷脂分子和大多数蛋白质分子都One of the world's great natural wonders is in New Mexico, in the southwest of America. Nature has created huge moving hills of pure white sand. These sand dunes cover more than seventy­thousand hectares of desert. It is one of the largest sand dune fields in the United States. The bright white sand dunes are always changing，always moving, like waves on the ocean.Driven by strong winds, the sand moves and covers everything in its path. It is like a huge sea of sand. You may wonder how anything can live in this extreme environment of a white sand desert. There is not much rain.The heat in summer is intense. The sand lacks nutrients.Plants and animals struggle to survive. A few kinds of plants grow quickly to survive burial by the moving sand dunes. Several kinds of small animals have become white in color in order to hide in the sand. More than five hundred thousand people visit White Sands each year. They climb on the dunes and observe the moving sea of sand. White Sands is about twenty four kilometers southeast of the city of Alamogordo, New Mexico. In the visitor center at the entrance of the park, you can find out special activities and guided walks. You can drive about thirteen kilometers into the center of the dunes. It is like driving on a lonely white planet.Along the way there is information that tells about the natural history of White Sands. You can also explore the dunes on foot, seeing some unusual and beautiful plants and flowers. Signs along the trail tell about the plants growing in the sand. You can even camp there overnight. But you must be careful. It is easy to get lost in the waves of moving sand especially during sandstorms. There is no water to drink. The temperature can rise to thirty eight degrees Celsius in summer. There is no shelter from the sun's rays. White Sands is part of America's National Parks System, and it is just one of the unusual examples of America's natural and cultural treasures. 16．Which of the following plays a major role in making for the extreme environment? A．Plants and animals. B．Strong winds. C．Intense heat and little rain. D．Many people. 17．Walking on dunes, people will ________． A．enjoy the beautiful sight of sand moving B．see many kinds of white plants and animals C．find out some special activities D．get lost easily and quickly especially during storms 18．What do we know about White Sands from this passage? A．It is one of the largest sand dune fields in the world. B．You can get to know its natural history while driving in it. C．The temperature here can rise to thirty­eight degrees Celsius any time. D．You are not allowed to camp here overnight. 19．What is the main purpose of the passage? A．To attract tourists to White Sands. B．To describe the history of White Sands. C．To introduce guided tours to White Sands. D．To explain the power of nature at White Sands.