题目内容
（请给出正确答案）
A、HMG CoA synthase
B、HMG CoA reductase
C、HMG CoA lyase
D、MVA kinase
E、squalene epoxidase
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更多“The key enzyme in cholesterol synthesis is”相关的问题
A、Phosphorylase
B、Hexokinase
C、Phosphoenol pyruvate carboxykinase
D、HMG-CoA reductase
E、Pyruvate kinase
A、Glucose kinase
B、Phosphofructokinase-1
C、Pyruvate kinase
D、Phosphoglycerate kinase
E、Fructose-1,6-bisphosphatase
A、All of them are the enzymes that catalyze intermediate reactions of metabolisms.
B、They have higher catalytic activities in enzyme systems.
C、The regulation of the enzyme activity does not affect the metabolic rate of the whole system.
D、All reactions catalyzed by key enzymes are reversible.
A、It is the key enzyme for glycogen decomposition.
B、There are two forms including phosphorylase a and phosphorylase b.
C、Phosphorylase a is inactive form.
D、Enzyme activity is regulated by hormones.
E、Phosphorylase b is activated by phosphorylase kinase.
A、Heme synthesis is affected by kidney and brain diseases
B、Heme is synthesized from succinyl-CoA, glycine and Fe2+
C、ALA synthase is the key enzyme for heme synthesis.
D、Heme is synthesized mainly in bone marrow and liver.
E、The initial reaction and the last three steps in the formation of porphyrins occur in mitochondria
听力原文： Let's begin today by discussing enzymes. Enzymes are what make many of the body's biochemical reactions possible. Actually biochemical reactions can take place without them, but at much lower rates. In fact an enzyme may cause a reaction to proceed billions of times faster than it would otherwise. Before I go on to the biochemical specifics of how this works, let me provide a figurative example. I think it will help illustrate the power of enzymes more clearly. Now, suppose you got a bag and you put a bunch of locks in it, just small padlocks. Then you put in all the keys that go with the locks. And you closed the bag and shook it hard. No matter how long you shook, chances are very small that any key would get inserted in any of the locks. But if you took them all out of the bag and this time used your hands to insert the keys in the locks, you could combine them much quicker.
Enzymes act like your hands, quickly allowing chemical reactions that would otherwise take much longer. Now, there are 2 reasons that enzymes are so effective at enabling biochemical reactions. Firs enzymes greatly reduce the amount of energy required to start the reactions, and with less energy needed the reactions can proceed a lot faster than they, could without the enzyme. The second mason is that on a small amount of an enzyme is needed to enable the biochemical reaction. That's because the chemical structure of the enzyme itself does not become altered as if enables the reaction. So a single enzyme can be used to start the same biochemical reaction over and over again.
(43)
A．The impact of enzymes on chemical reactions.
B．The way the body produces enzymes.
C．The structure of enzymes.
D．Types of chemical products created with enzymes.
从键盘输入一个英文字母，如果它是大写英文字母，则将其转换为小写英文字母，如果它是小写英文字母，则将其转换为大写英文字母，然后将转换后的英文字母及其ASCII码值显示到屏幕上，如果不是英文字母，则不转换直接将它及其ASCII码值输出到屏幕上。按要求在空白处填写适当的表达式或语句，使程序完整并符合题目要求。#include ＜stdio.h＞ int main() { char ch; printf("Press a key and then press Enter:"); ch = getchar(); if (____________) ch = ch + 32; else if (________________) ch = ch - 32; printf("%c, %d\n", ch, ch); return 0; }
A、第8行： ch ＞= 'A' && ch ＜= 'z' 第12行： ch＞= 'a' && ch ＜= 'z'＞ B、第8行： ch ＞= A && ch ＜= z 第12行： ch＞= a && ch ＜= z＞ C、第8行： ch ≥ 'A' && ch ≤ 'Z' 第12行： ch ≥'a' && ch ≤ 'z'
D、第8行： ch ≥ A && ch ≤ Z 第12行： ch ≥ a && ch ≤ z
阅读下列程序，写出程序执行后数据段BUF开始的10个内存单元中的内容。
DATASEGMENT
BUF DB08H，12H，34H，56H，78H，9AH，0BCH，0DEH，0F0H，0FFH
KEY DB78H
DATAENDS
CODESEGMENT
ASSUME CS：CODE，DS：DATA，ES：DATA
START： MOVAX，DATA
MOVDS，AX
MOVES，AX
CLD
LEA DI，BUF
MOVCL，[DI]
XORCH，CH
INC DI
MOV AL，KEY
REPNESCASB
JNE DONE
DECBUF
MOVSI，DI
DECDI
REP MOVSB
DONE： MOVAH，4CH
INT 21H
CODE ENDS
ENDSTART
执行结果：BUFDB _______ 、 _______、 _______ 、 _______、 _______、 _______、 _______、 _______、 _______ 、 _______。
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