Four step sequence that adds 2 carbons to an existing acyl chain (Skeleton):
(addition and modification of malonyl-CoA ) Existing acyl chain + malonyl-CoA, 2 carbons + 3 carbons = 4 carbons???? Decarboxylation removes 1 carbon as CO2 (the same carbon we added to create malonyl-CoA, same added as removed). Fatty acid synthesis requires that Malonyl-CoA is activated and fatty acid synthase, a large complex. Sequence: (1) condensation, 3C + 2C à 4C + CO2 leaves (2) reduction, NADPH + H+ is oxidized to NADP+, double bond is removed (3) dehydration, H2O leaves and another double bond is created somewhere else (4) reduction, NADPH + H+ is oxidized into NADP+ à saturated acyl group, lengthened by two carbons.