<prompt> Major form of folic acid to transfer one carbon isMethylene THFFormyl THFMethyl THFAll  <response>: The folic acid is first reduced to 7,8-dihydrofolic acid and fuher reduced to 5,6,7,8-tetrahydrofolic acid THFA Fig. 34.17. Both reactions are catalyzed by NADPH dependent folate reductase. B. TThe folic acid is first reduced to 7,8-dihydrofolic acid and fuher reduced to 5,6,7,8-tetrahydrofolic acid THFA Fig. 34.17. Both reactions are catalyzed by NADPH dependent folate reductase.The THFA is the carrier of one-carbon groups. One carbon compound is an organic molecule that contains only a single carbon atom. The following groups are one carbon compounds: i. Formyl -CHO ii. Formimino -CHNH iii. Methenyl -CH iv. Methylene -CH2- v. Hydroxymethyl -CH2OH vi. Methyl -CH3.he THFA is the carrier of one-carbon groups. One carbon compound is an organic molecule that contains only a single carbon atom. The following groups are one carbon compounds: i. Formyl -CHO ii. Formimino -CHNH iii. Methenyl -CH iv. Methylene -CH2- v. Hydroxymethyl -CH2OH vi. Methyl -CH3.Ref: DM Vasudevan - Textbook of Biochemistry, 6th edition, page no: 401 