Fatty acid synthesis is the process by which cells create fatty acids, which are essential components of lipids and serve as energy sources. This process primarily occurs in the cytoplasm of cells, where acetyl-CoA is converted into long-chain fatty acids through a series of enzymatic reactions. The key enzyme involved is fatty acid synthase, which catalyzes the addition of two-carbon units to build the fatty acid chain. The synthesis of fatty acids is regulated by various factors, including the availability of nutrients and hormones like insulin. This process is crucial for maintaining energy balance and supporting cellular functions, as fatty acids are vital for forming cell membranes and signaling molecules.