题干

叶绿体中的色素为脂溶性,液泡中紫红色的花青苷为水溶性.以月季成熟的紫红色叶片为材料,下列实验无法达到目的是(  )

A:用无水乙醇提取叶绿体中的色素

B:用水做层析液观察花青苷的色素带

C:用质壁分离和复原实验探究细胞的失水与吸水

D:用光学显微镜观察表皮细胞染色体的形态和数目

上一题 下一题 0.0难度 选择题 更新时间:2019-02-12 11:25:20

答案(点此获取答案解析)

D

同类题2

阅读理解

    I was at my parent's dinner table. Before me was a worn journal of thin and discolored pages. It was my grandfather's journal and now belonged to my father. My grandfather had passed away in the months leading up to my birth. I never got to visit the places he had frequently and people who had been a part of his life's journey.

    I was now about to enter his world, through the words he had left behind. Within minutes, I was attracted by the power of the written words. In the magical script before me, I was transported to another age when food was an everyday art, planned, prepared and enjoyed in the company of others, and a time when people had the heart to pause,their own lives to embrace (拥抱)each other's struggles. All this was conveyed to me in the beauty of the words that flowed together to connect with the writer's mind and understand the world they lived in.

    That kind of writing seems to be lost on us today. We have gotten used to writing in bite-sized pieces for a public looking for entertainment, and hungry for information. No wonder, there are nearly 200 million bloggers on the Internet and a new blog is created somewhere in the world every half a second. Instead of adding to our collective wisdom, most of these writings reflect the superficiality (肤浅)and impatience of our day and age.

    This not only robs us of the skill of writing impressive essays, it also prevents us from exploring what is truly important. Writing humbles us in a way that is vital for our character growth, by reminding us about the limits of the self and our appropriate place in the vast flow of life. Writing frees us by helping us explore the unknown so that we truly open up to the magic of the world around us. I saw all of this in the writing s of my grandfather. And I've seen it again and again in the writings of the greatest thinkers of humanity. Their writings reflect deep thought on issues of human importance.