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【简答题】
基本建设的含义是固定资产的扩大在生产的 、 、 、 之相连带的其他工作。
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皮皮学刷刷变学霸
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【简答题】在“氧气、氮气、二氧化硫、二氧化碳、稀有气体”中选择适当的物质填空： （1）用于制造硝酸和化肥的是______； （2）引起温室效应的主要气体______； （3）空气中含量较多且化学性质比较活泼的气体______； （4）可制成五光十色霓虹灯的是______．
【多选题】What is the biological and pharmaceutical role of D-amino acids?
A.
Although D-amino acids do not generally occur in proteins, they do serve some special functions in the structure of bacterial cell walls and peptide antibiotics.
B.
Bacterial peptidoglycans contain both D-alanine and D-glutamate. D-Amino acids arise directly from the L isomers by the action of amino acid racemases, which have pyridoxal phosphate as cofactor. Amino acid racemization is uniquely important to bacterial metabolism, and enzymes such as alanine racemase are prime targets for pharmaceutical agents.
C.
One such agent, L-fluoroalanine, is being tested as an antibacterial drug. Another, cycloserine, is used to treat tuberculosis.
D.
Because these inhibitors also affect some PLP-requiring human enzymes, however, they have potentially undesirable side effects.
【简答题】What are amino acids?
【单选题】What has a significant position in the growth of human body tissues?
A.
Essential amino acids.
B.
Non-essential amino acids.
C.
Fat.
D.
Proteins.
【单选题】空气里含有①氧气、②氮气、③稀有气体、④二氧化碳及其它气体和杂质，这些气体在空气中的体积分数按由大到小顺序排列正确的是（ ）
A.
①②③④
B.
②①③④
C.
①②④③
D.
②①④③
【单选题】空气中的氮气、氧气、二氧化碳和稀有气体的体积百分比依次为 ( )o
A.
(A)87．08％、11．90％、0．03％、0。99％
B.
(B)78．08％、11．90％、3．3％、6．72％
C.
(C)68．08％、20．90％、6．72％、4。3％
D.
(D)78．08％、20．90％、0．03％、0．94％
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