Fatty acid synthesis begins with a preparatory step in which acteyl CoA is transferred from mitochondria to the cytoplasm. However, it cannot pass through the membrane, so it is transported as citrate, which is cleaved to acteyl CoA and oxaloacetate. In the cytosol, acetyl CoA is converted to malonyl CoA, a three-carbon compound. Fatty acid synthesis begins with the transfer of the acetyl group from acetyl CoA to fatty acid synthase. 3- carbon groups, supplied by malonyl ACP, are added to the growing acyl chain in a series of steps involving condensation, reduction, and dehydration reactions. Elongation of the fatty acid chain stops at 16 carbon atoms, after 7 cycles, as the free fatty acid is released.
Fatty acid synthesis is the process that uses end products of carbohydrate’s catabolism (acetyl CoA is produced from pyruvate, while pyruvate is produced by the oxidation of glucose in glycolysis) are converted to fatty acids. This process is reverse to β-oxidation.
Produced fatty acids can be esterified with glycerol to form the triacylglycerols that are then packaged in VLDL and secreted from the liver.
