Choose the one best answer that most accurately describes some properties of acetyl-CoA carboxylase.

Biotin is required for the acetyl-CoA carboxylase reaction in which the substrate, acetyl-CoA, is carboxylated by the addition of CO2 to form malonyl-CoA. This reaction occurs in the cytosol. Malonyl-CoA provides the C-2 units that add to the growing fatty acid chain on the fatty acid synthase complex. As the growing chain is elongated, malonyl-CoA is decarboxylated. Citrate is an allosteric activator of the enzyme, and the enzyme is inhibited by phosphorylation by the AMP-activated protein kinase.