試題詳解

43. Folic acid is required for nucleotide synthesis. Which of the following statements about folic acid is incorrect?

(A) Folic acid is a cofactor in many metabolic reactions involving one-carbon (methyl-, methylene-, formyl-) functional groups.
(B) These one-carbon functional groups are usually modified at the N5 or NI0 position of folic acid.
(C) Sulfonamide inhibits bacterial growth by inhibiting the formation of para- amino benzoic acid (PABA), a precursor of folic acid.
(D) Tetrahydrofolate is the activated form of folic acid. The hydrogens are normally added to N5, C6, C7, and N8 of folic acid.
(E) The cancer chemotherapeutic drug methotrexate is similar in structure to folic acid and can inhibit the synthesis of tetrahydrofolate.