Final answer:
The cofactor required for the conversion of DHF to THF is NADPH, with ascorbic acid also playing a supportive role in this essential biological process. This conversion is critical for nucleotide synthesis and amino acid metabolism.
Step-by-step explanation:
The cofactor needed for dihydrofolate (DHF) to be converted to tetrahydrofolate (THF) is NADPH. This reduction reaction is catalyzed by the enzyme dihydrofolate reductase. In addition to NADPH, ascorbic acid can also play a supportive role in this process. Tetrahydrofolate is a vital molecule in the body, necessary for various reactions, including the synthesis of purines and the conversion of serine to glycine. A deficiency in the conversion of DHF to THF can lead to problems such as megaloblastic anemia.