Fatty acid synthesis

Fatty acids are formed by the action of Fatty acid synthases from acetyl-CoA and malonyl-CoA precursors. In humans fatty acids are predominantly formed in the liver and adipose tissue, and mammary glands during lactation. Most of acetyl-CoA is formed by Acetyl Co-A synthetase in the mitochondria and is transported into cytosol in the form of citrate.

Elongation
Much like β-oxidation, elongation occurs via four recurring reactions:

In the second step of elongation, butyryl ACP condenses with malonyl ACP to form an acyl ACP compound. This continues until a C16 acyl compound is formed, at which point it is hydrolyzed by a thioesterase into palmitate and ACP.