Active metabolite form in synthesis of fatty acid is:-

Staing material in FA synthesis is Acetyl CoA Acetyl CoA (2C) - Malonyl CoA -Used for FA Synthesis Malonyl CoA is the Main active metabolite used. Each time during elongation of fatty acid chain the addition of 2C carbons taking place are derived from malonyl CoA. So, it the active metabolite of fatty acid synthesis.