Fatty acid biosynthesis is similar in all known prokaryotes and eukaryotes. In eukaryotes, the biosynthesis of a fatty acid such as palmitate (C16) occurs in the cytoplasm. The basic strategy includes the following three possible steps:

1) Synthesis of Palmitate from Acetyl-CoA

2) Chain Elongation of Palmitate (long chain fatty acids)

3) Fatty Acid Desaturation

Though the reactions in fatty acid biosynthesis resemble the reversal of the analogous reactions in oxidation, fatty acid synthesis is distinct from fatty acid oxidation (Figure 18.23). For example, acyl groups are carried by acyl carrier protein in fatty acid synthesis, instead of coenzyme A. Furthermore, reducing equivalents come from NADPH and energy is provided by ATP. Overall, the biosynthesis of palmitate from 8 acetyl-CoAs requires 7 ATPs and 14 NADPHs.

Most of the enzymatic activities required for the synthesis of palmitate from acetyl-CoA are found on a multienzyme complex called fatty acid synthase that is composed of two polypeptide chains.

Oxidation of Saturated Fatty Acids