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【多选题】
How do aromatic amino acids serve as precursors of many plant compounds?A.
Phenylalanine, tyrosine, and tryptophan are converted to a variety of important compounds in plants.
B.
The rigid polymer lignin, derived from phenylalanine and tyrosine, is second only to cellulose in abundance in plant tissues. The structure of the lignin polymer is complex and not well understood.
C.
Tryptophan is also the precursor of the plant growth hormone indole-3-acetate, or auxin, which is important in the regulation of a wide range of biological processes in plants.
D.
Phenylalanine and tyrosine also give rise to many commercially significant natural products, including the tannins that inhibit oxidation in wines; alkaloids such as morphine, which have potent physiological effects; and the flavoring of cinnamon oil, nutmeg, cloves, vanilla, cayenne pepper, and other products.
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A.
它为血液中CO2运输的一种形式
B.
它仅运送CO2总量的7％
C.
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D.
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A.
E 为杆的抗拉（压）刚度
B.
乘积 EA 表示材料抵抗拉伸（压缩）变形的能力
C.
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D.
以上说法都不正确