问题 单项选择题

三羧酸循环中底物水平磷酸化的反应是()

A.柠檬酸→α-同戊二酸

B.琥珀酰CoA→琥珀酸

C.琥珀酸→延胡索酸

D.延胡索酸→苹果酸

E.苹果酸→草酰乙酸

答案

参考答案:B

解析:三羧酸循环中只有一步底物水平磷酸化,就是琥珀酰CoA生成琥珀酸的反应。

问答题 简答题
单项选择题

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Newspapers have one basic (4) , to get the news as quickly as possible from its source, from those who make it to those who want to (5) it.
Radio, telegraph, television, and (6) inventions brought competition for newspaper. So did the development of magazines and other means of communication. (7) , this competition merely spurred the newspapers on. They quickly made use of the newer and faster means of communication to improve the (8) and thus the efficiency of their own operations. Today more newspapers are (9) and read than ever before. Competition also led newspapers to branch out into many other fields. Besides keeping readers (10) of the latest news, today’s newspapers (11) and influence readers about politics and other important and serious matters. Newspapers influence readers’ economic choices (12) advertising. Most newspapers depend on advertising for very (13) .
Newspapers are sold at a price that (14) even a small fraction of the cost of production. The main (15) of income for most newspapers is commercial advertising. The (16) in selling advertising depends on a newspaper’s value to advertisers. This (17) in terms of circulation. How many people read the newspaper
Circulation depends (18) on the work of the circulation department and on the services or entertainment (19) in a newspaper’s pages. But for the most part, circulation depends on a newspaper’s value to readers as a source of information (20) the community, city, county, state, nation, and world—and even outer space.

[A] measures[B] measured [C] is measured [D] was measured