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问题 单项选择题 A1型题

酶活性测定的反应体系的叙述正确的是（）

A.底物浓度与酶促反应速度呈直线函数关系

B.温育时间必须在120分钟以上

C.反应体系中不应该用缓冲溶液

D.在0～40℃范围内，反应速度随温度升高而加快

E.pH为中性

答案

参考答案：D

解析：本试题考核酶活性测定条件及相关知识。影响酶促反应的各种因素是设计酶活性测定反应体系的基础。当其他因素固定在最适（佳）条件时，底物（作用物）浓度与酶反应速度呈双曲线型，可用米-曼方程来表示，而不是直线关系，所以备选答案A叙述错误。不同的酶有不同的最适pH，不一定为中性；为维持反应体系pH稳定，酶反应应在一定缓冲溶液中进行；反应时间因酶而异，凡临床检测或国际生化与分子生物学会酶学分会有规定"标准方法"均应按规定时间及各项条件进行反应。可见，备选答案B、C、E叙述错误。唯有D叙述，即在0～40℃范围内，反应速度随温度升高而加快，这对绝大多数酶促反应是正确的，因此是最佳参考答案：。

单项选择题

下列属于A类IP地址的是______。

A．61.11.68.1

B．128.168.119.102

C．202.199.15.32

D．294.125.13.1
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单项选择题

Lobbying groups often try to disguise a financial self-interest by clumsily dressing up their arguments in the guise of concern for the public. You see this tendency in the pharmaceutical industry (21) in energy and lumber companies who like to tout their (22) of the environment. But (23) , two new books argue, are these tactics more (24) a cause for concern than in agribusiness.
Marion Nestle’s "Food Safety: Bacteria, Biotechnology, and Bio-terrorism’ looks at the way the American meat and biotechnology industries have (25) successfully on Capitol Hill (26) stricter federal regulation, which the author argues has undermined the safety of the food supply.
(27) , Maxime Schwartz’s "How the Cows Turned Mad" (28) the origins of mad-cow disease over more than two centuries, and reveals the fallout from the British government’s blind (29) that the disease could not be (30) to humans.
In 1999, Ms Nestle writes in her earlier book, Rosemary Mueklow, the executive director of the National Meat Association, lobbied against President Clinton’s (31) to establish a more thorough testing regime for E. coli 0157: H7, a potentially (32) pathogen.
Ms Muck low’s organization—which represents meatpackers and processors who (33) to discard or reprocess meat found to be infected under the new testing regime—argued on Capitol Hill that (34) microbial testing in meat could actually lead to a greater public health risk (35) confident consumers might relax their own safe-handling procedures at home.

A. against B. with C. toD. over
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