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问题 单项选择题

下列关于NAD和NADP的描述，哪一项是正确的（）。

A.NAD是单核苷酸，NADP是二核苷酸

B.NAD含尼克酰胺，NADP含尼克酸

C.NADP分子含有2’，5’－二磷酸核糖；NADP分子含有5’－磷酸核糖

D.NADH可以作为谷光甘肽还原酶的辅酶；NADP可作为乙醇脱氢酶的辅酶

E.NAD是辅酶II，NADP是辅酶I

答案

参考答案：C

选择题

读“地球五带图”回答（共5分）。

（1）右图中界线F的名称是            。

（2）请用斜线画出有极昼、极夜现象的范围。

（3）你家乡处于五带中的             带。

有阳光直射的是                 带。
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单项选择题

About fifty years ago, plant physiologists set out to grow roots by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and the usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along fine on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require energy, of course. The process of respiration uses sugar to make the high energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen.The study of isolated roots has provided an understanding of the relationship between shoots and roots in intact plants. The leaves of the shoots provide the roots with sugar and vitamins, and the roots provide the shoots with water and minerals. In addition, roots can provide the shoots with organic nitrogen compounds. This comes in handy for the growth of buds in the early spring when leaves are not yet functioning. Once leaves begin photosynthesizing, they produce protein, but only mature leaves can "export" protein to the rest of the plant in the form of amino acids.

It can be inferred from the passage that, in the early spring, the buds of plants________.

A．export protein in the form of amino acids

B．do not require water

C．have begun photosynthesizing

D．obtain organic compounds from the root
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