試題詳解

30. The synthesis of purine and pyrimidine nucleotides differ in that:
(A) pyrimidine biosynthesis is
tightly regulated in the cell, whereas purine biosynthesis is not.
(B) ATP is required in the
synthesis of purines but not in the synthesis of pyrimidines.
(C) pyrimidines go through many
steps, adding a single carbon or nitrogen each time, whereas the basic skeleton for purines is
formed by two main precursors.
(D) purine formation requires a THF derivative, whereas
pyrimidine formation does not.
(E) purine biosynthesis starts with the formation of PRPP,
whereas pyrimidines incorporate the PRPP near the end of the pathway.