各种蛋白质的含氮量很接近,平均为( )
A. 19%
B. 18%
C. 17%
D. 16%
E. 15%
Which description is wrong about RNA? ( )
A. mRNA contains codons
B. There are three main classes of RNA molecules, mRNA,tRNA and rRNA
C. rRNA is a component of ribosomes
D. RNA with the maximum molecular weight is tRNA
which metabolic pathway provide the energy for mature red blood cells? ( )
A. aerobic oxidation of glucose
B. oxidation of fatty acids
C. anaerobic oxidation of glucose
D. PPP
Which vitamine is essential for methionine cycle?()
A. biotin
B. vitamine B12
C. vitamine B2
D. pyridoxal
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