酶化学习题 一、选择题
1、Zn是糖酵解中的醛缩酶的辅基，该酶没有和Zn结合时应该被称作:
2+
2+
A) B) C) D) E) Apoenzyme（脱辅基酶蛋白）. Coenzyme（辅酶）. Holoenzyme（全酶）. prosthetic group（辅基）. Substrate（底物）.
2、Enzymes are potent（高效的） catalysts（催化剂） because they:
A) are consumed in the reactions they catalyze（催化）.
B) are very specific and can prevent the conversion of products back to substrates（底物）. C) drive reactions to completion while other catalysts drive reactions to equilibrium（平衡）. D) increase the equilibrium constants（平衡 常数） for the reactions they catalyze. E) lower the activation energy（活化能） for the reactions they catalyze. 3、用米氏方程测定的是反应初速度，其有利之处是在反应刚开始时:
A) [ES] can be measured accurately.
B) changes in [S] are negligible（可以忽略的）, so [S] can be treated as a constant（常数）. C) changes in Km are negligible, so Km can be treated as a constant. D) V0 = Vmax.
E) varying [S] has no effect on V0. 4、根据酶促反应动力学，在平衡状态时:
A) Km = Ks.
B) the enzyme is regulated.
C) the ES complex is formed and broken down at equivalent rates. D) the Km is equivalent to the cellular substrate concentration. E) the maximum velocity occurs when the enzyme is saturated. 5、Which of these statements about enzyme-catalyzed reactions is false?
A) At saturating（饱和） levels of substrate, the rate of an enzyme-catalyzed reaction is
proportional to the enzyme concentration.
B) If enough substrate is added, the normal Vmax of a reaction can be attained even in the
presence of a competitive inhibitor.
C) The rate of a reaction decreases steadily with time as substrate is depleted.
D) The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction,
but the equilibrium constant is more favorable in the enzyme-catalyzed reaction. E) The Michaelis-Menten constant Km equals the [S] at which V = 1/2 Vmax. 6、通过双倒数作图测定Km 时，应该:
A) Multiply（乘以） the reciprocal（倒数） of the x-axis intercept（截距） by 1. B) multiply the reciprocal of the y-axis intercept by 1. C) take the reciprocal of the x-axis intercept. D) take the reciprocal of the y-axis intercept. E) take the x-axis intercept where V0 = 1/2 Vmax.
7、The number of substrate molecules converted to product in a given unit of time by a single enzyme molecule at saturation（饱和） is referred to as the:
A) dissociation constant（解离常数）. B) maximum velocity（最大速度）.
C) Michaelis-Menten number（米氏常数）. D) turnover number（转换数）.
10、在酶促反应双倒数作图中，竞争性抑制剂使：
A) y-轴上的截距变小. B) y-轴上的截距不变. C) X轴上的截距不变. D) X轴上的截距变大. 11、酶促反应的Vmax:
A) 随 pH升高而增大。
B) 在竞争性抑制剂时存在时会增大。 C) 只和反应的底物浓度有关。
D) 在反竞争性抑制剂存在时会变小。 12、下列哪类物质为酶的不可逆抑制剂？
A)有机磷农药 B)抗生素磺胺药物 C)抗肿瘤药物甲氨蝶呤 13、有关变构酶，下列说法错误的是：
A) Allosteric effectors give rise to sigmoidal V0 vs. [S] kinetic plots（变构剂使
酶促反应速度-底物浓度曲线为S曲线）.
B) Allosteric enzymes are generally composed of several subunits. C) An effector may either inhibit or activate an enzyme.
D) Binding of the effector changes the conformation of the enzyme molecule. E) allosteric effectors compete with substrate for binding sites（结合位点）.
二、符号解释
LDH Km 三、名词解释 酶
酶的活性中心
酶促反应动力学
米氏常数
酶的转换数
酶原激活
关键酶 同功酶 酶活力
四、简答题
1.简述酶与一般催化剂的主要区别。
2.有机磷、重金属以及磺胺类药物分别为哪种酶的抑制剂？它们分别属于哪类抑制剂？
