Final answer:
Intermediates in fatty acid biosynthesis are attached to the acyl carrier protein (ACP), which is part of the fatty acid synthase complex. The growing fatty acid chain is bonded to ACP's phosphopantetheine group, and the entire process requires NADPH as a reducing agent, eventually producing palmitoyl-ACP.
Step-by-step explanation:
The intermediates in the biosynthesis of fatty acids are attached to a molecule known as the acyl carrier protein (ACP). This protein contains a phosphopantetheine group, which has an active sulfhydryl (-SH) group that forms a thioester bond with the fatty acid intermediate. Along with ACP, the enzyme ketoacyl-ACP synthase (KS) also contains a cysteine residue with a sulfhydryl group that plays a critical role in the elongation process of the fatty acid chain.
During fatty acid synthesis, the growing fatty acid chain remains linked to the phosphopantetheine group of ACP. This synthesis continues through multiple cycles, each adding two carbons to the chain until a 16 carbon fatty acid, palmitoyl-ACP, is produced. This process requires NADPH as a reducing agent and involves enzymes such as acetyl-CoA carboxylase (ACC) for the initial steps.