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【单选题】
关于心包说法正确的是（）。A.
心包腔在浆膜心包与纤维心包之间
B.
浆膜心包位于心外膜外面
C.
纤维心包又分脏壁两层
D.
有浆膜心包和纤维心包
E.
以上都不对
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皮皮学刷刷变学霸
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【简答题】当今的世界三大饮料包括（ ）。A. 可乐B. 可可C. 咖啡D. 茶叶E. 奶茶
【多选题】How are purine and pyrimidine bases recycled by salvage pathways?
A.
Free purine and pyrimidine bases are constantly released in cells during the metabolic degradation of nucleotides. Free purines are in large part salvaged and reused to make nucleotides, in a pathway much simpler than the de novo synthesis of purine nucleotides described earlier.
B.
One of the primary salvage pathways consists of a single reaction catalyzed by adenosine phosphoribosyltransferase, in which free adenine reacts with PRPP to yield the corresponding adenine nucleotide.
C.
Free guanine and hypoxanthine (the deamination product of adenine ) are salvaged in the same way by hypoxanthine-guanine phosphoribosyltransferase.
D.
A similar salvage pathway exists for pyrimidine bases in microorganisms, and possibly in mammals.
【简答题】A．points B．stations C．establishments D．bases