This document summarizes lipid metabolism. It begins by defining lipids and their main functions in energy storage, cell structure, and signaling. It then overviews lipid digestion, which involves emulsification by bile salts and hydrolysis by pancreatic lipase. Absorbed lipids are transported by chylomicrons to the liver. The document also summarizes beta-oxidation of fatty acids, which occurs through activation, transport into mitochondria, and four cyclic steps. Ketone bodies are formed from acetyl-CoA and serve as an alternative fuel for tissues during fasting. In summary, the document outlines the key processes of lipid digestion, transport, breakdown and energy production.