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【单选题】
一般展示空间的的通道宽度是按人流数计算的,一股人流等于一个人的肩膀宽度,其数值约为()。
A.
70cm
B.
60cm
C.
80cmm
D.
100cm
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【单选题】Most differentiated animal cells are polarized; that is, one end of the cell is structurally or functionally different from the other. Cells specialized for secretion have their _________________ posi...
A.
endoplasmic reticulum (ER)
B.
Golgi apparatus
C.
mitochondria
D.
endosomes
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【判断题】三相笼型异步电动机的电气控制线路，如果使用热继电器作过载保护，就不必再装设熔断器作短路保护。    (    )
A.
正确
B.
错误
查看完整题目与答案
【判断题】The tissue-cell specificity of biological development is based on the fact that cells in different tissues have different genomes.
A.
正确
B.
错误
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【单选题】某种产品耗用的A材料是分工序投入，各工序的投料方式为一次性投入，各工序的A材料的消耗定额为：第一道工序20千克，第二道工序20千克，第三道工序10千克。该产品第二道工序在产品的投料率为( )。
A.
40%
B.
80%
C.
60%
D.
50%
查看完整题目与答案
【单选题】While there are 20 amino acids commonly found in proteins, over 300 different amino acids have been identified in cells. Which of the following is NOT created by a post-translational modification?
A.
Selenocysteine
B.
4-hydroxyproline
C.
γ-Carboxyglutamate
D.
5-hydroxylysine
查看完整题目与答案
【多选题】How do different types of muscle cells perform different functions?
A.
The highly specialized contractile machinery in muscle cells is thought to have evolved from the simpler contractile bundles of myosin and actin filaments found in all eukaryotic cells. The myosin-II in nonmuscle cells is also activated by a rise in cytosolic Ca 2+ , but the mechanism of activation is different from that of the muscle-specific myosin-II. An increase in Ca 2+ leads to the phosphorylation of nonmuscle myosin-II, which alters the myosin conformation and enables it to interact with actin.
B.
A similar activation mechanism operates in smooth muscle, which is present in the walls of the stomach, intestine, uterus, and arteries, and in many other structures that undergo slow and sustained involuntary contractions. This mode of myosin activation is relatively slow, because time is needed for enzyme molecules to diffuse to the myosin heads and carry out the phosphorylation and subsequent dephosphorylation.
C.
However, this mechanism has the advantage that—unlike the mechanism used by skeletal muscle cells—it can be activated by a variety of extracellular signals: thus smooth muscle, for example, is triggered to contract by epinephrine, serotonin, prostaglandins, and several other signal molecules.
D.
In addition to skeletal and smooth muscle, other forms of muscle each perform a specific mechanical function. Heart—or cardiac—muscle, for instance, drives the circulation of blood. The heart contracts autonomously for the entire life of the organism—some 3 billion (3 × 10 9 ) times in an average human lifetime. Even subtle abnormalities in the actin or myosin of heart muscle can lead to serious disease. For example, mutations in the genes that encode cardiac myosin-II or other proteins in the sarcomere cause familial hypertrophic cardiomyopathy, a hereditary disorder responsible for sudden death in young athletes.
查看完整题目与答案
【单选题】某种产品耗用的A材料是分工序投入,各工序的投料方式为一次性投入,各工序的A材料的消耗定额为:第一道工序20千克,第二道工序20千克,第三道工序10千克。该产品第二道工序在产品的投料率为()
A.
80%
B.
40%
C.
60%
D.
50%
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【单选题】Different types of cells in an organism have ___
A.
the same set of DNA
B.
the same set of mRNA
C.
different set of DNA
D.
different set of mRNA
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【判断题】[电气控制类]三相笼型异步电动机的电气控制线路，如果使用热继电器作过载保护，就不必再装设熔断器作短路保护。
A.
正确
B.
错误
查看完整题目与答案
【简答题】NADPH and NADH have different roles in cells.
查看完整题目与答案
相关题目：
【单选题】Most differentiated animal cells are polarized; that is, one end of the cell is structurally or functionally different from the other. Cells specialized for secretion have their _________________ posi...
A.
endoplasmic reticulum (ER)
B.
Golgi apparatus
C.
mitochondria
D.
endosomes
查看完整题目与答案
【判断题】三相笼型异步电动机的电气控制线路，如果使用热继电器作过载保护，就不必再装设熔断器作短路保护。    (    )
A.
正确
B.
错误
查看完整题目与答案
【判断题】The tissue-cell specificity of biological development is based on the fact that cells in different tissues have different genomes.
A.
正确
B.
错误
查看完整题目与答案
【单选题】某种产品耗用的A材料是分工序投入，各工序的投料方式为一次性投入，各工序的A材料的消耗定额为：第一道工序20千克，第二道工序20千克，第三道工序10千克。该产品第二道工序在产品的投料率为( )。
A.
40%
B.
80%
C.
60%
D.
50%
查看完整题目与答案
【单选题】While there are 20 amino acids commonly found in proteins, over 300 different amino acids have been identified in cells. Which of the following is NOT created by a post-translational modification?
A.
Selenocysteine
B.
4-hydroxyproline
C.
γ-Carboxyglutamate
D.
5-hydroxylysine
查看完整题目与答案
【多选题】How do different types of muscle cells perform different functions?
A.
The highly specialized contractile machinery in muscle cells is thought to have evolved from the simpler contractile bundles of myosin and actin filaments found in all eukaryotic cells. The myosin-II in nonmuscle cells is also activated by a rise in cytosolic Ca 2+ , but the mechanism of activation is different from that of the muscle-specific myosin-II. An increase in Ca 2+ leads to the phosphorylation of nonmuscle myosin-II, which alters the myosin conformation and enables it to interact with actin.
B.
A similar activation mechanism operates in smooth muscle, which is present in the walls of the stomach, intestine, uterus, and arteries, and in many other structures that undergo slow and sustained involuntary contractions. This mode of myosin activation is relatively slow, because time is needed for enzyme molecules to diffuse to the myosin heads and carry out the phosphorylation and subsequent dephosphorylation.
C.
However, this mechanism has the advantage that—unlike the mechanism used by skeletal muscle cells—it can be activated by a variety of extracellular signals: thus smooth muscle, for example, is triggered to contract by epinephrine, serotonin, prostaglandins, and several other signal molecules.
D.
In addition to skeletal and smooth muscle, other forms of muscle each perform a specific mechanical function. Heart—or cardiac—muscle, for instance, drives the circulation of blood. The heart contracts autonomously for the entire life of the organism—some 3 billion (3 × 10 9 ) times in an average human lifetime. Even subtle abnormalities in the actin or myosin of heart muscle can lead to serious disease. For example, mutations in the genes that encode cardiac myosin-II or other proteins in the sarcomere cause familial hypertrophic cardiomyopathy, a hereditary disorder responsible for sudden death in young athletes.
查看完整题目与答案
【单选题】某种产品耗用的A材料是分工序投入,各工序的投料方式为一次性投入,各工序的A材料的消耗定额为:第一道工序20千克,第二道工序20千克,第三道工序10千克。该产品第二道工序在产品的投料率为()
A.
80%
B.
40%
C.
60%
D.
50%
查看完整题目与答案
【单选题】Different types of cells in an organism have ___
A.
the same set of DNA
B.
the same set of mRNA
C.
different set of DNA
D.
different set of mRNA
查看完整题目与答案
【判断题】[电气控制类]三相笼型异步电动机的电气控制线路，如果使用热继电器作过载保护，就不必再装设熔断器作短路保护。
A.
正确
B.
错误
查看完整题目与答案
【简答题】NADPH and NADH have different roles in cells.
查看完整题目与答案