Lipolysis

Lipolysis is the enzymatic breakdown of stored triglycerides into fatty acids and glycerol. In adipose tissue, it releases fatty acids for use as fuel and glycerol for metabolism.

Adipose triglyceride lipase: An enzyme that initiates triglyceride breakdown by releasing a fatty acid from a triglyceride molecule. It catalyzes the first step of stored triglyceride breakdown in adipocytes.
Triglyceride: A lipid molecule consisting of glycerol esterified to three fatty acids. This is the principal stored substrate that lipolysis cleaves.
Beta oxidation: A metabolic pathway that sequentially cleaves two-carbon units from fatty acids to form acetyl-CoA. It converts lipolysis-derived fatty acids into a form that can feed energy metabolism.
Lipogenesis: The synthesis of fatty acids and their incorporation into storage lipids. It builds lipid stores, opposing the mobilization performed by lipolysis.
Hormone-sensitive lipase: An enzyme that hydrolyzes diacylglycerols and other lipid esters, with activity regulated by hormonal signals. It performs a major intermediate step after adipose triglyceride lipase acts.
Adipocyte: A specialized cell that stores energy primarily as triglycerides in lipid droplets. Adipocytes are the main site of regulated mobilization of stored fat.
Ketogenesis: The production of ketone bodies from acetyl-CoA, mainly in liver mitochondria. During prolonged fasting, fatty acids released by lipolysis help supply ketone-body production.
Lipid digestion: The enzymatic breakdown and absorption of dietary fats in the digestive tract. It hydrolyzes dietary lipids in the gut, unlike mobilization of stored cellular triglycerides.
Monoacylglycerol lipase: An enzyme that hydrolyzes monoacylglycerols into glycerol and free fatty acids. It completes the principal sequence by releasing the final fatty acid and glycerol.
Lipid droplet: An intracellular organelle with a neutral-lipid core surrounded by a phospholipid monolayer and associated proteins. Stored triglycerides are packaged here, where lipases gain regulated access.

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